Field Validation Exercise

Transcription

1 Field Validation Exercise Background: When creating complex GIS databases, it is essential that all or a significant portion of the digitized (or acquired) data should to be validated; this is done with various methods but the most common is field validation, visiting the location and comparing GIS data to your observations. Remote Sensing often calls this process ground-truthing. To accomplish verification you have to have some very detailed version (copy) of your data available in the field to compare with your observations. You also need a process to record the results of your observations. You then transfer these results back to the office, integrating the observed field fixes into your data base on an office or cloud database. Your task is to perform a field validation of two of your data layers students will validate grate presence and absence, to ensure that the grates you interpreted on your study area and from the data truly are grates. You should pick at about 20 grates to visit, and verify that you ve properly identified them. You should make sure to include any grates you were unsure of when you digitized them. You should also walk as much of your study area as you can, to look for grates you might have missed. Each visited grate should have a checked/verified attribute in your data layer students should also observe the canopy in their study area, 1) to look for new plantings, and 2) to verify the interpretation on conifer/hardwood for their canopy. Identify 10 trees crowns to specifically verify students should validate sewer grate presence and absence, to ensure that the grates you interpreted on your study area and from the data truly are grates. You should pick at about 20 grates to visit, and verify that you ve properly identified them. You should make sure to include any grates you were unsure of when you digitized them. You should also walk as much of your study area as you can, to look for grates you might have missed students should also validate land cover in their study area, by pervious surface type. Visit about 20 points selected at random in your study area, and identify it as impervious (concrete, building, asphalt, etc.) or pervious (grass, flower bed, shrubs, pervious pavers). Links to resources, and following description of tools: ES File Explorer: GPS Test PDF Maps General

2 Getting started: Prepare your data within a GIS to use in the field. This could be a very detailed printed copy of a map of your study area or some electronic version (hand-held device). The key issue is that all of the data you need to verify should to be OBVIOUS on the map or easily found on the handheld device. This means that scale is very important. You must print a very detailed large-scale map or have the ability to change the scale on your hand-held device. (zoomin). The common issue with exporting data is to render your data at a level of detail to support the required scale change (zoom-in/out). 1 st step: Prepare a map of your study area (or the area in which you will perform the validation). Create a layout, and export a GeoPDF of your area using ArcGIS. PDF s are useful as you can provide details of many relevant layers. Use of aerial imagery is also common but often you need to limit the amount of information to just what is needed for validation and for related layers to maintain your orientation. Export the PDF in the highest resolution possible at the largest scale possible. In this example, I used a tabloid size at 600 DPI. You should also ensure that the Advanced Tab (Export Map as PDF) is set to Export Map Georeference Information

3 Oct nd Step: Move the PDF to the hand-held device. There are several methods to move a PDF (in this case a geospatially enabled or GeoPDF) to a hand-held. A common approach is to the PDF as an attachment. For this example we use and App that transfers files over a FTP WiFi connection. Using an Android based device, Nexus 7, start the installed App ES File Explorer. If you do not see a screen that looks like the one to the right, swipe across the screen to display the desktop with ES File Explorer. Below (left), find the down arrow in the middle of the screen and it will bring up a full screen; like the one on the right. Select the View on PC tool. Select the View on PC tool.

4 On the left screen (below) tap the blue button at the bottom Turn On Then note the ftp address. Shown to the right is an EXAMPLE, your numbers will be similar but not exactly the same. This is an FTP address. On your computer (on the same WiFi as the hand-held) navigate to File Explorer (not an internet browser). Type in the search bar EXACTLY what you see on the hand-held eg: ftp:// :3721/ You will now see the contents of the hand-held (as shown above right). Copy your geo PDF map of your area to be verified to the PDFMaps folder on the hand-held device. Remember the ES File Explorer connection process as you will use the opposite to copy your field verified data from the hand-held to your computer. On the handheld, open PDF Maps and add the PDF map you just transferred (see next page).

5 Import your PDF map from the PDFMaps folder on the hand-held unit. When finished importing, open the PDF and explore the map.

6 Oct An example of a geospatially enabled PDF map in Avenza Maps (PDF Maps) Zoom in or pan around. Find the features you wish to verify. Notice the cursor (above) is colored in orange. The cursor color is user selectable. Use your finger to move the map around under the cursor. Verifying points (pins) will only be dropped at the cursor location. If you drop a pin right now, it will be located at your cursor location. Pins are dropped by tapping the pin icon at the top left. When you have an active GNSS position, and you are on the map, it will display as a Blue Dot If you walk around on the map the Blue Dot moves displaying your current position. If you wish to drop a pin at your current position you need to center the cursor (now shown in BLACK) over the Blue Dot. You do this by pressing the target icon. Then drop the pin Practice dropping a pin, You should erase practice work before field verifying your features.

7 As you drop a pin select the right arrow to open the detail screen verification This detail screen the Placemark screen. We will use a custom with attribute appropriate generic screen for To delete a pin aka Placemark, select the trash icon in the upper right of the Edit Map Feature, when Placemark detail is displayed Custom Attributes: For our work we will be collection verification details for several different types of features. For each type we should first create a folder and then add unique detailed attributes to the features within that folder. For example: Folder: Canopy Attributes: Type, string Choices: Conifer, Broadleaf Height, decimal Verified, Boolean ( this means Yes or No) Date, string Folder: SewerGrate Attributes: Verified, Boolean Date, string Folder: Building Attributes: Roof Type, string Choices: Flat, Pitched, Steep Pitched Height, decimal Verified, Boolean Date, string You can create these folders and add the attributes yourself or load the.kml file provided Data Verify Exercise Tabloid.kml

8 To add your own: select the Pin list from the top menu and then select Then hamburger button at the bottom right. Then select Add Folder (not shown here); remember to select the check mark to complete each step. Add as many folders and need. Having separate folders will help you later just export the Pins (Placemarks) you want. Now you will select each folder (one at a time) and add the attributes. To Select a folder from the list, do a LONG press, that will turn the folder title YELLOW. Then select the PENCIL icon in the upper toolbar to add your attributes. My empty folder: Here, I long pressed and selected the Pencil icon

9 Now press the Plus by Attribute Schema. Add your attributes (if you wish) Then add a new folder and add attributes to that new folder. Repeat as often as needed. Here is my completed: Folder List Remember to LONG press to enter the folder and select the pencil icon for edit. Here is my Buildings folder attributes: Notice that the Choices for the Roof Type or the Yes/No of the Verified does not show here. The choices only come up when you need them at entry time. (if you want to you can touch the entry for Roof Type and see or change the details). Next validation data in the field. Remember you have folders for each type of verification. You will only be able to drop a pin in to one folder at a time. This means you must REMEMBER WHICH FOLDER IS CURRENT. At the folder level there is a listing for SET TO CURRENT FOLDER,

10 Press that and it will CHANGE to CURRENT FOLDER You can also change the colors of the pins if you wish. Now with your folder current, add pins for that verification type. For each pin complete all the attributes. If you make a mistake, you can select the individual pin within a folder and LONG PRESS, then using eht MOVE FOLDER icon, move it to another folder. If you do move points, the attributes might need to be re-entered or corrected. To send your data back to your GIS. There are several steps: 1. At the Map Features (list of folders) select the hamburger icon and select Export Map Features. 2. Now you have to select File Name for Export what you want your output to be called). 3. Select Export Format. You can send out KML but you lose your attribute data. To send out each record with the attributes, select CSV 4. Select Send To: here you want Device Storage but you can it to yourself 5. Now what to Export, if you select visible only you can control the grouping of the output. If you export everything, it will send all the records for each folder, all together and you will have to sort it out in ArcMap. The best approach is back a step. At the folder list LONG PRESS on each folder and select the eyeball icon at the top to make all the records in that folder NOT VISIBLE. If you leave one folder VISIBLE and the others NOT VISIBLE you can control the export process. Remember to check the Export visible only box on the Export Map Features screen. 6. Repeat the connection with ES File Explorer and copy the exported files to your computer. To Load CSV files into ArcMAP In ArcMap tables in several formats can be loaded; CSV, Text, Excel, dbase, etc. You add the your CSV table to the ArcMap Table of Contents (TOC). Open

11 the table and make sure you understand the headings and all the information is present. Then Use the FilleàAdd X, Y data menu selection to add the table to the map.

12 You have indicate which is the X value and which is the Y value. Also, you have to state the projection/datum that the table is using. Most commonly external CSV, KML & GPX files are in Geographic (WGS84). Select OK to the Object-ID warning p Add X,Y data to ArcMap DOES NOT CREATE A SHAPEFILE. THE LOADED TABLE IS A EVENT You must select the event and EXPORT DATA to a Shapefile.

13 Finally, you have many choices to choose how you add (combined) the field data with your GIS data layers. You can APPEND DATA or transfer the data manually, or do an Identity, Spatial Join (recommended) and then use Field Calculator to update fields. Note: if you are attempting to perform a Spatial Join between Sewer Grates (as Points) and Verified Sewer Grates (as Points), you may need specify a Search Radius.