Celebrating Our Woodland Heritage QGIS Manual

Transcription

1 0 Celebrating Our Woodland Heritage: QGIS Manual Celebrating Our Woodland Heritage QGIS Manual Pennine Prospects Celebrating Our Woodland Heritage Project

2 1 Celebrating Our Woodland Heritage: QGIS Manual Celebrating Our Woodland Heritage QGIS Manual Pennine Prospects Celebrating Our Woodland Heritage Project Compiled by Christopher Atkinson BA (Hons), MA Woodland Heritage Officer Celebrating Our Woodland Heritage Project December 2017 Pennine Prospects Hebden Bridge Canal & Visitor Centre Hebden Bridge West Yorkshire HX7 8AF

3 2 Celebrating Our Woodland Heritage: QGIS Manual About the Author and Pennine Prospects At the time of this report s production, the author Christopher Atkinson was in employment with Pennine Prospects as part of the Celebrating Our Woodland Heritage Project. As Woodland Heritage Officer, Chris was tasked with carrying out a programme of archaeological woodland surveys across the South Pennines. Chris has been in full time employment as an archaeologist since 2006, during which time he has been employed by Herefordshire Council s archaeology service as Community Archaeologist ( ); Project Officer for the National Trust (2015) and self-employed ( ). He is experienced in landscape survey, site excavation, geophysical survey, deskbased assessment, use of GIS techniques (including MapInfo Professional; ArcGIS and QGIS) and the production of management plans for clients such as Natural England and Historic England. Chris holds an undergraduate degree in Archaeology from the University of Wales Lampeter (2004) and a Masters with distinction in Landscape Archaeology from the University of Sheffield (2015). Pennine Prospects is a unique rural regeneration company created in 2005 as a champion for the South Pennines, the dramatic upland landscape that stands prominently above the urban centres of Greater Manchester, the Lancashire valleys and West Yorkshire. It is an award-winning partnership organisation that has attracted over 5 million of national and European funding to deliver a wide range of projects aimed at promoting, protecting and enhancing the built, natural and cultural heritage of the South Pennines. Pennine Prospects lies at the heart of a well-established partnership bringing together six local authorities, two water companies, government agencies and the voluntary sector. The company is strongly committed to sustainable development and enables partner organisations, local residents and businesses to maximise the benefit of the area s rich natural, cultural and heritage assets. Through its activities, Pennine Prospects supports the economy of the South Pennines by uncovering, highlighting and promoting all that is special about the area. In addition, the company develops community projects, promotes access to the uplands and waterways and connects people with their landscape.

4 3 Celebrating Our Woodland Heritage: QGIS Manual Contents Introduction 1.0 Setting Up A New Project Using Vector Data 2.1 Importing Vector Data Managing Vector Data Labelling Vector Data Adding Attributes to Vector Data Creating Point Vector Data from Survey Data Creating Polygon Vector Data Using Raster Data 3.1 Importing Raster Data Georeferencing Raster Data Using Light Detection and Ranging (LiDAR) 4.1 Importing LiDAR Data Slope Modelling Hillshade Modelling Creating and Saving a Map 5.1 North Arrow Scale Bar Legend Text Box Save Map 39

5 4 Celebrating Our Woodland Heritage: QGIS Manual Introduction This report has been compiled as part of the Celebrating Our Woodland Heritage project. This three year project ( ) is jointly funded by Yorkshire Water, Heritage Lottery Fund, Green Bank Trust and Newground Together and aims to identify record and interpret the historic environment of woodlands across the South Pennines (National Character Area 36 Natural England, 2014). Led by Pennine Prospects, the project recognises as a result of a desk-based study Hidden Heritage of the South Pennine Woodlands (Brown, 2013), that number of sites recorded on the HER (Historic Environment Record) does not represent the true nature of the surviving archaeological resource. The report highlighted that this underrepresentation (and general lack of knowledge) was the primary threat to woodland archaeology. The Celebrating Our Woodland Heritage project therefore seeks to enhance the historic record for woodland across the South Pennines by means of a structured programme of archaeological walkover surveys. Where appropriate these surveys will provide the opportunity for members of the public, heritage and youth groups to engage and contribute towards the investigations. Archaeological features to be recorded within areas of woodland can represent the whole of human history and use of the landscape. Features relating to the woodland itself can include historic or veteran trees; woodland boundaries; charcoal burning platforms; storage platforms; cottage sites; trackways and mills. Features may also predate the current woodland and represent prehistoric-medieval field boundaries; settlement sites or stones such as Bronze-Age cup and ring carvings. The information collated during the field surveys will be deposited in the form of an archaeological report and digital record to the landowner and the regional Historic Environment Record. This data will not only guide future research into the region, but also support and promote the preservation of the historic environment as a part of any future management programmes within woodlands. This manual is aimed at individuals interested in enhancing their archaeological skills providing an introduction to Geographical Information Systems (GIS) and its uses in archaeology.

6 5 Celebrating Our Woodland Heritage: QGIS Manual QGIS is a great piece of Open Source (FREE) software that meets all the basic mapping and analysis requirements of most archaeologists. It offers individuals a platform to visualise survey data, display mapping data (such has historic maps) and utilise Light Detection and Ranging (LiDAR) files produced by the Environment Agency and now made Open Source. Ultimately GIS is a tool, providing the individual with the opportunity to store, edit, analyse, display, share and publish their investigations at a professional standard. From landscape surveys and field walking to geophysical surveys and excavations, GIS software is a must have tool in the archaeologists arsenal. To follow this guide you can download the Open Source digital files from the Celebrating Our Woodland Heritage project website at: Below is a useful list of links from which you can obtain all of the Open Source data you require to get you started on your own GIS projects: GIS Software Download QGIS for your platform Opendata Ordnance Survey Data LiDAR and Orthophotographic Data Historic England Listing Data Natural England Data Historic Maps Please be a aware of copyright infringements regarding the use of historic maps

7 6 Celebrating Our Woodland Heritage: QGIS Manual 1.0 Setting up a new project Open QGIS Desktop with GRASS (you may have to wait a couple of minutes for the software open). Close the QGIS Tips window when it opens. Figure 1: You should see a window like this above To begin click on Project (found in the horizontal toolbar at the top of the page) and select Project Properties (figure 1). A window will open, from which you can set the basic requirements of the new project (figure 2). First visit CRS (listed on the left hand side). This allows you to set the Coordinate Reference System. First tick Enable on the fly CRS transformation (OTF) which means you can use data which have multiple coordinate systems in the same project. We will be using the British National Grid as our coordinate system. Find OSGB 1936 / British National Grid EPSG: from the list and select Apply (if searching for the first time you may have to check the Coordinate reference systems of the world box).

8 7 Celebrating Our Woodland Heritage: QGIS Manual Figure 2: Project Properties CRS Then select General from the left hand side of the Project Properties window. Here we need to make sure the Save Paths option is set to relative (figure 3). Doing this allows us to move a folder from one location to another without breaking file links. Press OK to finish Figure 3: Project Properties General When complete, click on Project and select Save As. Save the file within the GIS Workshop Data folder under the name Hirst Wood.

9 8 Celebrating Our Woodland Heritage: QGIS Manual 2.0 Using Vector Data What is Vector Data? Vector data provides a way to represent real world features within the GIS environment. A feature is anything you can see on the landscape. A vector feature has its shape represented using geometry. The geometry is made up of one or more interconnected vertices. A vertex describes a position in space using an X, Y (Easting and Northing) and optionally Z axis (Height). A feature with a single vertex (such as a find spot, tree or charcoal platform) is known as a point feature. Where a feature s geometry consists of two or more vertices and the first and last vertex are not equal (such as a river, track, ditch or boundary) a polyline feature is formed. Where three or more vertices are present, and the last vertex is equal to the first, an enclosed polygon feature is formed (such as an area of woodland, lake or building). Vector data also includes attributes, which consist of text or numerical information that describe the features. Point Data Polyline Data Polygon Data 2.1 Importing Vector Data On the saved Hirst Wood project select the Add Vector Layer icon (figure 4). This will open the Add vector layer window (figure 5), click Browse and select the Natural England Data (figure 6) and then Clipped Ancient Woodland v3.shp. Figure 4

10 9 Celebrating Our Woodland Heritage: QGIS Manual Figure 5 Press Open on the Add Vector Layer window. After a moment you should see a scattering of polygons relating to the location of semi-ancient natural woodland across the South Pennines. Figure 6 We will now start to build up our map of Hirst Wood. Following the same routine as above we will now select the OS Opendata 50m Contour folder and import the vector layer SE13_line.shp. You will notice a grid of contour lines appear on your map. To zoom in on this layer, right click on the layer labelled SE13_Line listed on the left of the screen in the Layers Panel and select Zoom to Layer (figure 7). Figure 7 We now need to add Ordnance Survey data relating to roads, buildings, railways, rivers and woodland. Repeat the process and select OS VectorMap District (ESRI Shape File) SE, then Data and open the layers:

11 10 Celebrating Our Woodland Heritage: QGIS Manual SE_Building.shp SE_RailwayTrack.shp SE_Road.shp SE_SurfaceWater_Area.shp SE_SurfaceWater_Line.shp SE_Woodland.shp Figure 8: On completion your map window should look something like this 2.2 Managing Vector Data You will notice that each of the shapefile layers added are a mixture of polyline and polygon data. Using the Layer Panel on the left of the screen we need to rearrange the data so that each layer is visible in its entirety. Left click and drag each layer so that the polygon data is at the bottom and the polyline data is at the top. Make sure the contour layer SE13_line is at the top. Figure 9

12 11 Celebrating Our Woodland Heritage: QGIS Manual Figure 10 Figure 10: Layer Properties window displaying style page We now need to change the colour of each layer. To do this either right click on a layer and select Properties from the drop down menu, or double click on the layer to open the Layer Properties window (figure 10). Open the properties window for the Polygon layer SE_Woodland and select Style to change the colour of the layer. You can either select a costum colour or use on of the predefined colours. When you are happy with the colour press OK. Press Save. Repeat the process for the other vector layers.

13 12 Celebrating Our Woodland Heritage: QGIS Manual Figure 11: On completion your map may resemble something like this. 2.3 Labelling Vector Data Selecting the SE13_line contour vector layer we will now display height data alongside the contours. This information is saved within the layers attributes. Reopen the Layer Properties window and select Labels (figure 12). Figure 12: Layer Properties window displaying labels page. In the top bar select Show labels for this layer and then Label with 1.2 PROP_VALUE. You can also select the colour and size of the text in this window. When

14 13 Celebrating Our Woodland Heritage: QGIS Manual complete click OK. 2.4 Adding Attributes to Vector Data Attributes within Vector Data are sub-sets of information unique to each point, polyline or polygon produced. At a basic level an attribute is a grid reference in the form of an easting and a northing. But attributes can also represent a sites name, and site type (such as woodland, field, moorland) and even descriptive information. We are going to add a new field to the SE_Woodland Attribute Table, this will allow us to label Hirst Wood. 1. Right click on SE_Woodland and select Open Attribute Table from the drop down menu. 2. Select the Toggle Editing Mode icon (a yellow pencil in the top left hand corner of the attribute table see below left). 3. Select the New Field icon (a small table with a yellow star towards the right of the menu bar see below right). 4. In the Add Field table write Name in the Name column, set the Type to Text (string) from the drop down menu and increase the Length from 0 to 50 and press OK (right). 5. Once complete Save the table and close it. 6. Using the Information icon click on the polygon of Hirst Wood.

15 14 Celebrating Our Woodland Heritage: QGIS Manual 7. Right click on the column Name in the Identify Results panel and select Edit Feature Form from the drop down menu. 8. Type Hirst Wood into the Name column and press OK. 9. Finally Save the edits and press the Toggle Edit Mode icon on the main project page to end editing session. You can now label the wood on the Map Window via the Labels page in Properties. Press Save. 2.5 Creating Point Vector Data from Survey Data As part of the Celebrating Our Woodland Heritage project we have been collecting information concerning previously unrecorded/unrecognised archaeological features within woodland. Many of the features have consisted of small to large scale quarries, charcoal burning platforms, trackways, drystone walls and woodland bank and ditches. As part of the recording process we have noted each features grid reference, its type, a general description and notes concerning its condition. All of this information is essential in understanding the history and condition of woodland archaeology across the region. The collated field data is transferred into a digital spreadsheet format for use in reports. This data can also be used to create point vector data, which can be overlain onto our GIS map layers. This is useful for accurately displaying the location of the identified archaeological features, as well as comparing the results with any historic map layers, aerial photographs and LiDAR tiles. To create Point Vector Data from an EXCEL Spreadsheet: 1. Open the EXCEL spreadsheet Hirst Wood Archaeological Survey Database and save it as a CSV (Comma Delimited) file (Figure 13). 2. In your QGIS project window, select the Add Delimited Text Layer icon found on the left had side of the window. 3. This will open the Create a Layer from a Delimited Text File window (figure 14). Click Browse to select your EXCEL CSV file. Make sure the CSV (comma separated values) box is ticked and the x field contains Easting and the y field Northing. Press OK. 4. The survey data should now be plotted on your map as dots (Figure 16).

16 15 Celebrating Our Woodland Heritage: QGIS Manual Figure 13: Save the Excel spreadsheet as a CSV file. Figure 14: Create a Layer from a Delimited Text File window.

17 16 Celebrating Our Woodland Heritage: QGIS Manual 5. If the data is not displayed, it probably means it has been created using the wrong Coordinate Reference System. To correct this, right click on the layer listed in your Layers Panel and select Set Layer CRS from the drop down menu. In the Coordinate Reference System Selector window change the CRS to OSGB 1936 / British National Grid EPSG: and press OK. 6. You now need to save the data as a Point Vector file (shapefile). Right click on the layer listed in your Layers Panel and select Save As (figure 15 below left). 7. This will open the Save Vector Layer file As window (figure 15 below right). Click Browse to choose a location and name for the file, make sure the CRS is set to OSGB 1936 / British National Grid EPSG: and press OK. 8. You have now created a Point Vector Layer. If you press the icon you will be able to open each point s attributes table and look at the information produced as a result of the survey. Figure 15 Press Save.

18 17 Celebrating Our Woodland Heritage: QGIS Manual Figure 16 We will now alter the way the Hirst Wood Archaeological Survey Database data is displayed by displaying numbers relating to Site Number and colours relating to Site Type, as listed in the datas attributes. 1. Open the layers Layer Properties and select Style. 2. From the dropdown menu at the top of the window select the option Categorized. 3. You will notice the window has changed. From the dropdown menu second from the top and named Column, select the title Site Type. 4. Click the button Classify at the bottom left hand corner of the large white box. This will result in a list of Site Types appearing alongside representative colours (you can change the colours here by double clicking each circle). 5. When you are happy press Apply and select the Labels tab from the left hand column. 6. Following the steps outlined on page 12-13, label the layer selecting Site No. 7. Press OK (Figure 17).

19 18 Celebrating Our Woodland Heritage: QGIS Manual Figure 17: Survey point vector data presented as categorised with Site Type represented as different colours and labelled by Site No. 2.6 Creating Polygon Vector Data Creating polygon vector data is really useful for highlighting areas of interest, such as the extent of an area of ridge and furrow identified during a survey; or the footprint of a building. As part of the Celebrating Our Woodland Heritage Project we have been creating polygon vector data shapefiles for the purpose of illustrating historic map data. Once historic maps have been georeferenced (See 3.2 Georeferenced Raster Data) creating polygon vector shapefiles for each map layer allows for the production of standardised map layers, ideal for reporting and publication. We will now import your the georeferenced raster map file Yorkshire Ordnance Survey Six-Inch England and Wales_modified contained within the COWH GIS Workshop Data (See 3.1 Importing Raster Data for directions). Once the historic map layers are display (make sure all other map layers are switched off) we need to create a New Shapefile Layer. 1. Press the New Shapefile Layer icon located near the bottom of the left column of the window. It should look like this:

20 19 Celebrating Our Woodland Heritage: QGIS Manual 2. This will open the New Shapefile Layer window (Figure 18). 3. Under Type, make sure Polygon is selected. 4. Beneath File encoding, select Project CRS (EPSG:27700 OSGB 1936 / British National Grid) from the drop down menu. 5. We now need to add New Fields before it is ready. These represent the polygon attributes. We want to add attributes/fields called Site Name and Type. 6. In the box listed as Name, type Site Name. 7. Make sure Text data is selected in the drop down menu under Type. 8. In the Length box change the number to 200 (this represents how many characters will be saved in the attribute/field, 200 is the maximum). 9. Press the Add to fields list. 10. Repeat for Type. 11. Press OK. 12. This will open the Save layer as window. Figure 18: New Shapefile Layer window 13. Save the file in the folder Hirst Wood Shapefiles as 1847 Ordnance Survey Six-Inch England and Wales. 14. A new layer should now appear in the Layers Panel called First County Series Survey. 15. We now need to add information to our Polygon Vector Data layer. To do this select the First County Series Survey in the Layers Panel and click on the Toggle editing icon (right).

21 20 Celebrating Our Woodland Heritage: QGIS Manual 16. Now click the Add Feature icon to begin. 17. This will activate a small crosshairs cursor on the map window. We will begin by zooming in on the site of New Hirst Mill (southwest corner of Hirst Wood) and mark the outline of the large mill structure (Figure 19). To do this hover the crosshairs over one corner of the building and left click. 18. This will place a vertex onto the location. As you move the cursor a thin red line will connect the cursor with the first vertex. Following the line of the wall in either a clockwise or anti-clockwise direction and click on the next corner to place another vertex. Repeat the process until all of the corners are marked and right click. 19. This will open a Feature Attributes window. In the box Site Name write New Hirst Mill (Disused). In the box Type, write Structure. Press OK Figure 19: Polygon of New Hirst Mill created Now repeat the process for other features recorded on the map. Only complete the Site Name box in the Feature Attributes window if the polygon created has a name (like New Hirst Mill, Mill Race, Weir or Hirst Wood). We don t tend to create polygons for trackways and roads as these will stand out once the surrounding polygons have been created. The polygon Types we use are: Water Structure

22 21 Celebrating Our Woodland Heritage: QGIS Manual Woodland Field Quarry Rough Pasture Moorland Recreation Ground 20. When complete, press the Save Layer Edits icon to save your work and select Toggle Editing icon to come out of editing mode. 21. As with point vector data, you can change the way they appear by going into Layer Properties (See below for example).

23 22 Celebrating Our Woodland Heritage: QGIS Manual 3.0 Using Raster Data What is Raster Data? In its simplest form, a raster consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information, such as temperature. Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps. A common use of raster data in a GIS is as a background display for other feature layers. For example, orthophotographs (photographs that are geometrically corrected) displayed underneath other layers provide the map user with confidence that map layers are spatially aligned and represent real objects, as well as additional information. Rasters are well suited for representing data that changes continuously across a landscape (surface elevation). They provide an effective method of storing the continuity as a surface. They also provide a regularly spaced representation of surfaces. Elevation values measured from the earth's surface are the most common application of surface maps, but other values, such as rainfall, temperature, concentration, and population density, can also define surfaces that can be spatially analysed. In archaeology we display Light Detection and Ranging (LiDAR) data as Rasters. 3.1 Importing Raster Data We will now import vertical aerial orthophotographs available from the Environment Agency. This data can serve as a basemap, as well as a way to check the accuracy of the vector data On the saved Hirst Wood project click the Add Raster Layer icon (figure 16). This will open the Open a GDAL Supported Raster Data Source window. Figure 16

24 23 Celebrating Our Woodland Heritage: QGIS Manual Search for the Environment Agency folder in the GIS Workshop Data and open the folder labelled Ortho-RGB-15CM-2007-SE13nw and select and Open the four files listed. Figure 17: Don t forget, as it is hiding all of the vector data, you may want to move the raster aerial photograph layer to the bottom in the Layer Panel. You will now be able to view the vertical aerial photograph data for Hirst Wood (figure 17) and its surroundings. To make this data more manageable, select each of the files labelled: Ortho_P _ _ _1m_res Ortho_P _ _ _1m_res Ortho_P _ _ _1m_res Ortho_P _ _ _1m_res Right click, and select Group Selected on the drop down menu. To rename the group, right click on the group title and select Rename from the drop down menu. Press Save.

25 24 Celebrating Our Woodland Heritage: QGIS Manual 3.2 Georeferenced Raster Data Raster files such as aerial photographs or images of historic maps can be imported into QGIS and georeferenced so that they can analysed alongside other raster data (such as LiDAR) and vector data (such as survey point data). We will attempt to georeference the PDF map Yorkshire Ordnance Survey Six-Inch England and Wales (copyright National Library of Scotland) using the vertical aerial photograph layers imported previously. 1. From the horizontal toolbar select Raster and then Georeferencer. 2. This will open the georeferencer window (figure 18). Figure 18: Georeferencer window. The raster logo on the left of the horizontal toolbar will open a browser window to open up your raster image. 3. Click on the Open Raster icon to search and load the map/image to be georeferenced. Select and open the PDF Yorkshire Ordnance Survey Six-Inch England and Wales. 4. Once the image is loaded, check the settings found along the menu toolbar at the top of the Georeferencer Window. From the dropdown menu select Transformation Settings. 5. In the Transformation Settings window check Transformation type is set to Polynomial 1; Target SRS is EPSG:27700 OSGB 1936/British National Grid.

26 25 Celebrating Our Woodland Heritage: QGIS Manual 6. Select Output Raster and ensure the File Name is: Yorkshire Ordnance Survey Six-Inch England and Wales_modified and press Save. 7. Ensure the box Load in QGIS when done is ticked. 8. Press OK (figure 19). 9. To begin select the Add Point Icon. 10. This will activate a crosshair cursor which you will use to select a location on the imported map which matches a location on the aerial photographs. The best places to selects are the corners of fields or corners of buildings; as well as the ends of bridges. 11. First select a location on the Dowley Gap Aqueduct at the western end of Hirst Wood. I have selected the point where the eastern bank of the River Aire meets the southern edge of the aqueduct, as this is unlikely to have altered significantly. 12. You will then be prompted to confirm the co-ordinates by a Enter Map Coordinates window. As we do not know the co-ordinates we will match the location with our aerial photograph. Select the From Map Canvas tab (figure 19). Figure 19: Once a point on the Raster image is selected click the From Map Canvas tab in the Enter Map Co-ordinates window. 13. You will then be returned to the main map window where you can select the same location on the aerial photograph. Try to be as accurate as possible

27 26 Celebrating Our Woodland Heritage: QGIS Manual with your selection, as any significant spatial differences between the two points will lead to a poorly georeferenced historic map. 14. When you select the location and left click you will be returned to the Georeferencer window and Enter Map Co-ordinates window where you can press OK to confirm the selection. 15. Repeat the process for at least four more locations, making sure to select locations around the area of Hirst Wood. 16. When complete select Start Georeferencing from the File dropdown menu. 17. After a short period of time the imported map image will be imported as a georeferenced image in the main map window. Close the Georeferencer Window and when prompted save the GCP points (the points selected for georeferencing). On completion the georeferenced historic map should look something like this (above). You can alter the transparency of the historic map layer from the Layer Panel.

28 27 Celebrating Our Woodland Heritage: QGIS Manual 4.0 Using Light Detection and Ranging (LiDAR) What is LiDAR? Airborne lidar (light detection and ranging) measures the height of the ground surface and other features in large areas of landscape with a very high resolution and accuracy. Such information was previously unavailable, except through labourintensive field survey or photogrammetry. It provides highly detailed and accurate models of the land surface at metre and submetre resolution. This provides archaeologists with the capability to recognise and record otherwise hard to detect features. Airborne LiDAR operates by using a pulsed laser beam fired from a plane. The beam is most commonly scanned from side to side as the aircraft flies over the survey area. It measures between 20,000 to 100,000 points per second to build an accurate, high resolution model of the ground and the features upon it (Historic England, 2017). Figure 20: Principals of LiDAR (Holden, 2002). LiDAR produced by the Environment Agency can be downloaded from the Government s Open Survey Data webpage in two forms. Digital Surface Model (DSM) A DSM is a model of the surface of the earth that includes all the features on it such as vegetation, buildings, cars etc.

29 28 Celebrating Our Woodland Heritage: QGIS Manual Digital Terrain Model (DTM) A DTM is a bare-earth model in which mathematical algorithms have been used to remove features such as vegetation and buildings (Great for identifying woodland archaeology). Depending on availability LiDAR DSM and DTM files can be downloaded at 0.25m, 0.50m, 1m or 2m resolution. The higher the resolution (i.e. 0.25m) the clearer the data and the more likely very subtle features will be identified across the landscape. Recognising Archaeological Features Here are some examples of archaeological features identifiable using LiDAR. Routes of Communication Terraced tracks and holloways are some of the easiest features to identify (below). They are often linear and link one area of activity with another. Quarries Mineral extraction sites (quarries) take on many forms. From small shallow delves or pits (below left) to large cuts exposing bedrock (below right). Platforms Platforms are either raised or terraced level surfaces. Platforms may have supported structures, temporary accommodation, working/storage areas or alternatively (depending on shape and size) may indicate locations of charcoal production.

30 29 Celebrating Our Woodland Heritage: QGIS Manual Walls Relict field boundaries or woodland boundaries can also be identified by means of LiDAR. 4.1 Importing LiDAR Data When downloaded, LiDAR data is in the format of an ASCII (American Standard Code for Information Interchange) file. In order to use these QGIS needs to convert them into a Raster format (Thankfully QGIS does this automatically). Before you begin, it is good practice to organise your folders to ensure all of your data does not get muddled up or lost! First open your folder GIS Workshop Data, right click and select New Folder. Rename it LiDAR Merge. We will use this folder to house our various LiDAR files. Open your Hirst Wood project to begin importing the LiDAR tiles: 1. Select the Add Raster Layer icon 2. Go to GIS Workshop Data, Environment Agency, LiDAR 1m DTM and select the four files: se1237_dtm_50cm.asc, se1238_dtm_50cm.asc, se1337_dtm_50cm.asc, se1338_dtm_50cm.asc and press Open. 3. The LiDAR DTM tiles should now visible on your map window (figure 21). If they are not, it probably means they have been imported using the wrong Coordinate Reference System. To correct this right click on each DTM tile listed in your Layers Panel and select Set Layer CRS from the drop down menu. In the Coordinate Reference System Selector window change the CRS to OSGB 1936 / British National Grid EPSG: and press OK.

31 30 Celebrating Our Woodland Heritage: QGIS Manual Figure 21: Imported LiDAR DTM tiles. 4. We now need to merge the four tiles into a single tile so that we can start to analyse the data. From the tool bar above the map window open Raster and from the drop down menu select Miscellaneous and then Merge (figure 22). 5. In the Merge window, where it reads Input Files, search for the four DTM files. In the Output File select your newly created LiDAR Merge folder and type Hirst Wood DTM 50cm Merge and press OK (figure 23). 6. The process may take a while and can sometimes crash! If it does, switch off the underlying layers and try again. 7. When complete, click Close on the Merge window. 8. The merged LiDAR DTM tile should now be visible on your map window (figure 24). If it is not, it probably means it has been imported using the wrong Coordinate Reference System. To correct this right click on the Hirst Wood DTM 50cm layer listed in your Layers Panel and select Set Layer CRS from the drop down menu. In the Coordinate Reference System Selector window change the CRS to OSGB 1936 / British National Grid EPSG: and press OK. 9. Press Save. Figure 22:

32 31 Celebrating Our Woodland Heritage: QGIS Manual Figure 23: Merge Window Figure 24: Map Window displaying the merged DTM tiles Hirst Wood DTM 50cm Merge

33 32 Celebrating Our Woodland Heritage: QGIS Manual 4.2 Slope Modelling Analysing LiDAR as a slope model, in essence calculates the slope severity for each of the cells which form the individual tiles. The visualisation of slope as part of our woodland surveys across the South Pennines is particularly useful as many of the woodlands are located on often steep valley slopes. This type of analysis is great at identifying features cut into these slopes such as trackways, platforms and quarries. It is less successful in the identification of more subtle features such as ridge and furrow and sometimes boundaries. To create a Slope Model with our merged LiDAR data: 1. From the tool bar select Raster, Terrain Analysis and Slope. 2. In the Slope window (figure 25), make sure the Elevation Layer is Hirst Wood DTM 50cm Merge. For Output Layer select the folder LiDAR Merge and type Hirst Wood DTM 50cm Slope and press Save. 3. Then press OK. 4. After a few moments is should load up, but you may have to change the CRS again (See below). Figure Using the icon drag a square over the area of Hirst Wood to zoom in (figure 26).

34 33 Celebrating Our Woodland Heritage: QGIS Manual Figure 26: Slope DTM Model of Hirst Wood. You should be able to see the individual trackways, quarries, platforms and boundaries within the woodland. The lighter colour represents slope whereas the dark colour represents a flat or gently undulating surface. 6. You can reverse these colours by right clicking on the layer in the Layers Panel and selecting Properties and then Style in the Layer Properties window. Change the Colour Gradient to White to Black in the drop down menu and press OK (figure 27). Figure 27: Reversing the colour may make features within the woodland easier to see.

35 34 Celebrating Our Woodland Heritage: QGIS Manual 4.3 Hillshade Modelling Hillshade analysis is the most common algorithm applied to LiDAR data. Each cell is given a shading value based upon a hypothetical light source. Relief is directly illuminated which makes it possible to recognise features. It is particularly effective for earthworks and subtle features such as ridge and furrow or largely ploughed out features. However, as it utilises a hypothetical light source, multiple algorithms will need to be applied in order to obtain a more complete understanding of a feature or landscape. To create a Hillshade Model with our merged LiDAR data: 1. From the tool bar select Raster, Terrain Analysis and Hillshade. 2. In the Hillshade window (figure 28), make sure the Elevation Layer is set to Hirst Wood DTM 50cm Merge. 3. In Output layer select the LiDAR Merge folder, type Hirst Wood DTM 50cm Hillshade and press Save. 4. The Illumination stats represent the direction from where the light source emanates (Azimuth) with 0 or 360 representing north. The Vertical Angle represents the height of the light source. These are the stats you can change in subsequent analysis. I always add these stats to the file title as a reminder. 5. Press OK. Figure 28: Hillshade Window Figure 29: Hillshade DTM of the merged Hirst Wood files.

36 35 Celebrating Our Woodland Heritage: QGIS Manual 5.0 Creating and Saving a Map Having loaded up some of our data we now want to create a map. This can be a bit awkward, but practice makes perfect. Remaining in the map window, reorganise your layers so that your Raster layers are at the bottom and your Vector Layers are on top. You may want to switch off your vector layers or alternatively change the way they appear. It is possible to change the transparency of a layer by opening up its Properties and selecting Style (figure 30). Figure 30: Here I have opened up the properties for the SE_Woodland layer and set the Layer Transparency to 90. The Hirst Wood map window once I have played with the settings of each layer.

37 36 Celebrating Our Woodland Heritage: QGIS Manual To create a map for publication you will need to access the Print Composer. 1. Select the New Print Composer Icon from the top menu bar. 2. Type Hirst Wood in the Composer Title window and press OK. This will open a map window titled Hirst Wood (figure 31). Figure 31: Map window 3. Select the Add new map icon from the top menu bar. 4. Place your cursor at a corner of the map page and then left click to mark a rectangle before releasing. This will import the map to the page (figure 32).

38 37 Celebrating Our Woodland Heritage: QGIS Manual We will now start to add core information to the map. 5.1 North Arrow 1. Select the Add Arrow Icon from the top menu bar. 2. Place your cursor over the map, left click and drag the mouse to draw a line, when ready release. 3. To change the line width or arrow size you can use the Arrow Properties window on the right hand side of the map window (figure 33 below). 5.2 Scale Bar 1. Select the Add New Scalebar Icon from the top menu bar. 2. Using your mouse, left click on the map and the scale bar should automatically appear in metres. 3. To change the style of the scale bar access the Item Properties listed on the right hand side of the map window (figure 34 below).

39 38 Celebrating Our Woodland Heritage: QGIS Manual 5.3 Legend 1. Select the Add New Legend Icon from the top menu bar. 2. Left click on the, map window where you would like it to appear. 3. You can control what appears in your Legend using the Item Properties listed on the right hand side of the map window. To do this you need to make sure the Auto Update box is not activated (figure 35). 4. You can then use the icons to add or remove items from the Legend box. Figure 35: 5. You can also change the name of each layer by highlighting a layer and clicking the icon. Type the new name in the window and press OK. On completion you map window should look something like this:

40 39 Celebrating Our Woodland Heritage: QGIS Manual 5.4 Text Box Adding a text box is important for making reference to the material displayed in the map. This map contains Ordnance Survey and Environment Agency data. 1. Using the GIS ACKNOWLEDGEMENT Word Document, Copy the acknowledgements for the OS Open Data and Environment Agency. 2. Click on the Add New Label Icon located in the top menu bar. 3. Paste the text from the GIS ACKNOWLEDGEMT Word Document into the Label Main Properties menu on the right hand side of the map window (figure 36). 4. The text will automatically load into the New Label box on the map. However you may need to change the size of the box using your cursor in order to see all of the text. Figure 36: 5. The text may be difficult to read as the box is transparent. To change this, scroll down the Label Main Properties until you find Background, and click on the box. This will provide your label with a white background. 5.5 Save Map When you are happy with your map, select Composer from the top menu bar and select Save Project from the drop down menu. This will save the map window as a template for any further mapping you wish to carry out. To save the map for publication and printing select Composer and select either Export as Image or Export as PDF from the drop down menu.