Geology & Geophysics REU GPS/GIS 1-day workshop handout #2: Importing Field Data to ArcGIS

Transcription

1 Geology & Geophysics REU GPS/GIS 1-day workshop handout #2: Importing Field Data to ArcGIS In this lab you ll start to use some basic ArcGIS routines. These include importing GPS field data and creating and populating shape files. I. STARTING ArcMap AND IMPORTING YOUR FIELD DATA Starting ArcMap and then adding data to a map are both activities that you will do many many times. The instructions are written for ArcGIS In other versions the commands and window labels may be slightly different, but they should be identifiable. 1. Open ArcMap: You will get an ArcMap Getting Started window. You ll see a file tree over on the left. Under New Maps you ll see Templates, and under Templates you ll see Standard Page Sizes. Under Standard Page Sizes, click on North American (ANSI) Page Sizes (you may not see the whole name). Over in the box on the right will be a number of choices. Click on Letter (ANSI A) Portrait. Click OK and you ll be in ArcMap! It should look somewhat like the following:

2 2 As you can see, there are lots of boxes, tabs, and icons. You can have way more than these if you really like lots of little windows on your screen. Note that way down in the lower left are some icons that are almost so small that they are unrecognizable. The left two of these will be used a lot because they allow you to switch between Data View (where you do most processing) and Layout View (where you pretty-up your data with scale bars, UTM grids, North arrows, etc.). For some reason, the default is to bring up a new map in Layout View, so click on the left-most of these tiny icons to switch to Data View: 4. There are two major boxes in the main ArcMap window. The one on the left looks more like a column and is labeled Table of Contents. Beneath this in a tall skinny box it says Layers. This is the more generic use of the word Layer, referring to different data sets that can be arranged, displayed, etc. We ll call this the Layer box. The Table of Contents window has 4 or 5 icons right under it, and you want to make sure that the left-most (List By Drawing Order) is selected. To the right is a larger box where things will eventually be displayed. We ll call this the Map box. The positioning of various menu items will likely be different than shown above. 5a) Notice that as you move the mouse around in the Map box, the coordinates are shown below, but that they don t make sense, plus it also says Unknown Units. b) In the Layer box, left-click twice slowly on the word Layers and you ll see that it becomes surrounded by a box, and a cursor starts flashing. Change its name to Waahila and click return.

3 You can change the names of all kinds of things in this manner, so it is useful to remember this process. 3 c) In the Layer box, right-click on Waahila, and select Properties You will get a Data Frame Properties window with lots of tabs. Click on the Coordinate System tab. In the Current coordinate system: box, it will say that there is No Coordinate system. In the unlabeled box in the top half of this window will be 3 folders, Favorites, Geographic Coordinate Systems, and Projected Coordinate Systems. Click the + signs next to Projected Coordinate Systems -> UTM -> NAD > NAD 1983 UTM Zone 4N. Before clicking OK, rightclick on NAD 1983 UTM Zone 4N and select Add to Favorites. Then click OK. Click OK. Now when you move the mouse around the Map window, you ll see more UTM-like numbers. Note that ArcGIS doesn t use UTM Zone characters, but instead uses N and S for Northern and Southern hemispheres. By defining the coordinate system before any data are imported, you are defining the default coordinate system of anything you import that doesn t already have a coordinate system. 6. Next, you will import the trackpoint shape file you created in GPS Utility. a) Click the Add Data button:. You will get an Add Data window that you use to navigate to the correct directory. In most (but not all) ArcMap and ArcCatalog operations, you don t actually see all your folders at first. In order to see a folder that is not displayed, click the Connect to Folder button: You will get a Connect to Folder window. Navigate to your Waahila folder, click on it, and then click OK. You will be back at the Add Data window, and in the dropdown button at the top (next to Look In: you should be able to navigate to your Waahila folder. When you get there, click on Waahila_trackpoints.shp and click Add. You will get an Unknown Spatial Reference window that is warning you that Waahila_trackpoints.shp doesn t have spatial reference information. Click OK. You could repeat for Waahila_waypoints.shp, but recall that GPS Utility doesn t actually save only the waypoints and instead lumps both the waypoints and trackpoints into one file. That s why we used Excel to save only the waypoints. However, as a.txt file, Waahila04.txt cannot be read directly into ArcGIS. b) Over on the right-hand side of your ArcMap screen is a little tab labeled Catalog (written vertically). Click on this and you ll see what looks kind of like Windows Explorer. It is somewhat unintuitive, but hopefully you ll be able to navigate to your Waahila folder within your REU folder. Once you get there, right-click on Waahila and select Refresh. You should see all the files that ArcGIS can recognize (even though, as mentioned above, it can t display them all).

4 c) Specifically, ArcMap cannot display.txt files, so you are going to have to convert Waahila04.txt to an ArcGIS shapefile. Right-click on Waahila04.txt and select Create Feature Class -> From XY Table You may get an error message. Because you forgot to close Excel. Click Cancel, close Excel, and try again. 4 d) You will get a Create Feature Class form XY Table window, and here you will tell Arc which columns in the file hold the easting and northing information. Click the dropdown button labeled X Field: and select easting. Click the dropdown button labeled Y Field: and select northing. You can leave the Z Field: choice as <None>. Then click the Coordinate System of Input Coordinates button e) You will get a Spatial Reference Properties window that should look a bit familiar. One difference will be that any coordinate systems that you ve already used will be listed under Favorites. Click on NAD 1983 UTM Zone 4N and then click OK. f) You will be back in the Create Feature Class From XY Table window. In the Output box, make sure that the file will be going to the correct folder (click on the folder icon to navigate to the right place if not), and name the file Waahila_waypoints2.shp and click OK. g) Arc will think a while and then create the shape file. If you go back into ArcCatalog and refresh the Waahila folder, you should see Waahila_waypoints2.shp. Click on Waahila_waypoints2.shp and drag it over to the Layers window. It will show up under Waahila_burnscar_trackpoints and more importantly, the waypoints will be displayed on your map. 7. Your data will show up in the Map box and the shape files will show up in the Layers box (but without their extensions). Note that Waahila_trackpoints is a polyline shape file, and Waahila_waypoints2 is a point shape file. Both have default symbology. Notice now that when you move the mouse around the screen you get units that are in meters, and should sound like familiar UTM values. a) Note that in our example, we set the defined coordinate system of the whole map before importing any data. The coordinate system we selected was the same as the shape file that we knew we were about to import. We could have imported the shape file without first defining a coordinate system for the whole map. If we did this, the map would adopt the coordinate system of the first data that are imported to it. I think it is good practice to define the coordinate system of a new map when you start out. b) Save your file! Click File -> Save or click the icon. Make sure it will go into your Waahila folder, and call it Waahila_map ArcMap files end in.mxd (but you don t have to add the.mxd). ArcMap map documents are not the actual data themselves. Instead it is a list of what is included in that map, pointers to where these data are, the symbology of various datasets, etc. For this reason, it is almost useless to ever only a.mxd file to someone because they likely won t have the same data, or if they do, the data will likely be in different folders, etc.

5 5 II. ArcCatalog 8. You used ArcCatalog a little bit already. You can either start it separately (the program icon looks like this: or, new (and better) in Arc 10.x, you will find an ArcCatalog tab over on the far right of the ArcMap window that looks like this: Most of the time you ll be able to use this tab in ArcMap, but now and then you ll have to open up ArcCatalog as a separate program (more on this later). Click on this tab. ArcCatalog looks somewhat like Windows Explorer, showing the files that you have in your Waahila folder (you may have to click on some + signs to see all the folder levels). Open Windows Explorer and navigate to your Waahila folder. You ll notice that there is not a 1:1 match between this and what you see in ArcCatalog. This is because ArcCatalog only shows you files that can be displayed in a map (or that can be converted to something that can be displayed on a map). A single shapefile will usually actually consist of 2, 5, or more individual files. This is why it is always better to delete shapefiles with ArcCatalog it makes sure to get all these individual files. To delete a file in ArcCatalog, right-click on it and select Delete. But remember in ArcCatalog, delete means delete the file will be gone for good! Note that if you Remove something from the Layers box of ArcMap, the file is not deleted, but instead it is only removed from the current map. VII A brief digression for some useful display tools 9. We forgot to explore how to look at things in the Map window. You should see, probably just under the main menu, a set of tools that looks like this: This is one of many toolbars, and it happens to be called Tools: They include a + magnifying glass (to zoom in), a - magnifying glass (to zoom out), a globe, etc. If you don t see this toolbar, click on Customize -> Toolbars -> Tools. The default is to have the Tools toolbar be grouped with all the icons up across the top. If you prefer to have this (or any) toolbar in its separate little window, click on the four dots at the far left of the toolbar and drag it somewhere into the map. If you want to change its shape, click on a corner and re-shape it. If the Tools toolbar ever disappears, on the very top menu line, click on Customize -> Toolbars -> Tools. The way the zoom-in tool works is that you click on the + magnifying glass, and then, holding the left mouse button, drag a box around the part of the image that you want to zoom in on. You can also zoom in and out by using the roller on the mouse.

6 6 The zoom-out tool is not so easy to use. You use it to draw a box (holding the left mouse button), and the smaller the box you draw, the more you zoom out. Instead, it is usually easier easiest to right-click on one of the layers over in the Layers box, and select Zoom To Layer. You will find yourself using this combination of the zoom tool and Zoom To Layer a lot, so get some practice using it. If a particular layer only occupies a small portion of the map, however, zooming to its extent still won t show you the whole map. If, however, you have a layer that is really large, you sometimes end up zooming out much farther than you intended. An example of this is when you use some of the State of Hawai i GIS data. There is a shapefile for parks, for example. It is the entire state. You might be only mapping Moloka i, but if you were to click on Zoom to Layer on the parks shapefile, it would zoom out to the entire state. Another way to zoom out is to click the little globe in the Tools window. This shows the extent of your whole map. But you can run into the same problem as when you use Zoom to Layer if you are using a dataset that is actually a lot bigger than your particular map project. 10. Another way to see a zoomed-in view is to use the magnifier. It is a little bit strange, and takes some getting used to. To use the magnifier, in the main ArcMap menu, click Windows -> Magnifier. You will get a Magnifier window. You move the magnifier around by clicking on the bar across the top, and dragging it to where you want to look. You can change the magnification amount by right-clicking on this bar, and sliding down to Properties The default is 400%. You can increase the size of the Magnifier window by clicking on a corner and dragging it. You close the magnifier by clicking on the x in its upper right corner. 11. Another super-useful thing to remember is that you can turn and off different items in the map. You do this by clicking the check box next to the layer name in the Layers box. If there is a checkmark in the box, the layer is being displayed. If not, it isn t. 12. If you decide you are never going to use a particular layer in your map again, you can remove it. Right-click on the layer and select Remove. Note that this does not delete the file. If you click Delete in ArcCatalog, however, that does delete the file, so it is important to keep these two straight! 13. You can also change the order that the layers are displayed (which is on top, which is below, etc.). You do this by clicking on the name of the particular layer, and sliding it up and down in the Layers box. Often you ll be puzzled about why you can t see a layer even though its box is checked. Usually the reason is that there is an opaque layer above it which is blocking everything below. Try sliding the layer you want to see all the way to the top. If you still can t see it, then the problem may be more serious.

7 7 III. DRAWING A SHAPE FILE 14. In 2007 there was a brushfire up on Waahila, and somebody crashed through the bushes to map its extent. The data were collected with a GPS and converted to an Arc point shapefile. The data are in the Waahila data directly as Waahila_burnscar_2007.zip Why a.zip file? Remember that a shape file in ArcGIS is always >1 file. If you have to transfer a shape file form one computer to another or if you are sending a shape file to someone else. The best way to make sure you actually send all the necessary files is to combine them into a.zip file. a) Copy Waahila_burnscar_2007.zip into your own Waahila directory and un-zip it. Right-click on Waahila_burnscar_2007.zip and select Extract All You will get an Extract Compressed (Zipped) Folders window. Click the Browse button to make sure that the destination will be your Waahila folder, and then click Extract. If you look in your folder you should see a whole bunch of Waahila_burnscar_2007 files. b) Click the Add Data button:. to pull Waahila_burnscar_2007 into your map. You ll see that it is a whole bunch of points. In actuality a burn scar is an area, so you are going to make a polygon shapefile for the burn scar. 15. BEFORE YOU CAN DRAW A NEW SHAPE, YOU HAVE TO CREATE THE EMPTY SHAPEFILE IN ARC CATALOG. THIS REQUIREMENT TO CREATE THE SHAPEFILE BEFORE YOU CAN DO ANYTHING WITH IT IS GUARANTEED SOMETHING THAT YOU WILL FORGET AT LEAST ONCE. a) In ArcCatalog find your Waahila folder and right-click on this name, and select New -> Shapefile You will get a Create New Shapefile window. In the Name: box, type burnscar and in the Feature Type: box, use the dropdown arrow to select Polygon. b) The Spatial Reference Description: box will say Unknown Coordinate System. Click Edit You will get a Spatial Reference Properties window, which by now should look familiar, so we won t repeat the instructions. At some point you will be back in the Create New Shapefile window, and the Spatial Reference Description: box will now have a whole bunch of stuff in it. Click OK. c) The burnscar shapefile will appear over in the Layers box of ArcMap with a default symbology (probably a sickly green box with black border). But there won t be anything displayed in the Map box because you haven t produced any data for it. You can turn the ArcCatalog window in ArcMap back into a tab on the right by clicking on the little icon in the upper right that looks like a push-pin (it is next to the x). If you accidentally click the x, the ArcCatalog window will go away completely. To get it back, click on the ArcCatalog icon along the top row:

8 Next it is time to populate your empty shapefiles with actual information. Essentially you will be drawing things, using the points as guides. ArcMap calls this process Editing. Drawing things such as this is an essential skill for geologic work. 8 16a) Zoom in so that the area of the burn scar (as outlined by the Waahila_burnscar_2007 points) occupies most of your Map box. b) Check to see if you have an Editor toolbox displayed. It will have an Editor button with a down-arrow, and a few other icons, all of which will be greyed-out. If no Editor toolbox is displayed, either click on the editor button: or click on Customize -> Toolbars -> Editor. c) In the Editor toolbar, click on Editor -> Start Editing. You will probably get a Start Editing window that is complaining about various layers being in different folders. Click on the burnscar shapefile and click OK. Next, will probably be another Start Editing window complaining about different data sets having different spatial references from the map. For now, don t worry about this, and click Continue. d) A Create Features window will show up, probably over on the right. The top part will eventually show all your shape files, but the first time you run Editor, it may be empty. If you don t see a Create Features window, click on Editor -> Editing Windows -> Create Features. After a few seconds you ll notice that the Create Features window has transformed into a tab over under the ArcCatalog tab. Click on the Create Features tab and the Create Features window will reappear. Notice to the right of where it says Create Features there is a little pushpin icon pointing to the left, and if you hover the cursor over this it will say Auto-hide. Click this icon and it will change to pointing down. More importantly the Create Features window will stop disappearing. If none of your shape files show up in the Create Features window (or in the future, if the shape file you want is not among those displayed in the Create Features window), you will need to create a Template. To do this, click on the Organize Templates button: at the top of the Create Features window. You will get an Organize Feature Templates window, and near the top, click on New Template. You will get a Create New Templates Wizard window, with all the shapefiles that are displayed in a list with click-boxes. Click all those that you expect to be editing (which means all of them for now), and then click Finish. You should be back at the Organize Feature Templates window, where you click Close. The shapefiles that you clicked should show up in the upper part of the Create Features window. The bottom part of the Create Features window will say Construction Tools. e) The Create Features window is where you tell ArcMap what shapefile you will be drawing something for. Therefore, it is important that you make sure you have the correct shapefile selected! Select burnscar.

9 17a) The two most useful geological drawing styles (= Construction Tools) are Polygon (or Line if you are drawing a line) and Auto Complete Polygon. Freehand is useful, but not if you ve had a lot of coffee. For now, select Polygon. 9 b) You use the Polygon tool by clicking the left mouse button on vertices along a path. Because ArcMap knows you are drawing what will eventually be a closed path (i.e., a polygon), it will start to close the path once you click the second vertex. As you click vertices around the burn scar, you do not need to click only on the trackpoints. You can click more frequently, less frequently, whatever. You should at least click on every inflection in the boundary, even the subtle ones. You ll see how it works pretty quickly. c) Click somewhere on the boundary of the burn scar. A rather annoying Feature Construction window will open up nearby, and as you click your way around the boundary, it will stay in front of where you are going. If you don t want this ridiculous little window constantly getting in your way, click on Editor -> Options You will get an Editing Options window. Click the General tab, and un-check Show mini toolbar. As soon as you click the third vertex, you ll see how Arc starts to close the polygon. You may be worried that this polygon has straight sides and that doesn t look very natural. Don t worry about this for now. d) If you make a mistake, the easiest thing to do is right-click somewhere, and select Delete Vertex from the menu that pops up. If you make a big mistake, right-click somewhere and select Delete Sketch from the menu, but be aware that the entire polygon will disappear, so you do not want to do this if you ve just spent 10 minutes (or hours) drawing a complicated shape! It is possible to go back later and edit individual vertices, so don t sweat getting them perfect. e) When you have clicked enough vertices to complete the burn scar polygon, right-click somewhere and select Finish Sketch. Your polygon will be shown with a bright cyan boundary and a little x in its middle. This is a view that you will see a lot. Any time something is shown with a cyan boundary, it means it has been selected. Being selected means different things for example, maybe you told Arc to find all the countries in a World_nation shapefile that begin with the letter A. In the editing case, with the cyan boundary and the little x, it means that the sketch has been completed, but it has not yet been saved. If you were to click the Delete key on your computer, the polygon will go away (forever!). If you click the Edit Tool (in the Editor toolbar), then you can click on the little x, and drag the polygon somewhere else in the map. It also means that you can make adjustments such as rounding the corners to make the polygon look more natural. 20 a) To make the corners rounded, you will need the Advanced Editing tools. Click on Editor -> More Editing Tools -> Advanced Editing. The default is to put these tools up next to the Editor toolbar.

10 10 b) Making sure that your polygon is still selected (cyan boundary and x in the middle), click on the Smooth tool: You will get a Smooth window with a Maximum allowable offset: box. The value you type will be the amount that the lines between vertices can be moved when the vertices are smoothed. The units are the units of the map, which in this case is meters. I have found that a value of 0.01 usually works best. Type in this value and click along the top line of the OK. If you don t like the result, click the Undo button ArcMap window. The Smooth tool is fine for isolated polygons (such as a single burn scar or a single lake), however, it is problematic when you have polygons that share boundaries (such as with geologic units). c) It is good practice to smooth your polygon when you make it because later on you may be drawing adjacent polygons and you ll want them to share boundaries without overlaps or gaps. If you try to smooth polygons after they ve been drawn nested to each other, they may not smooth identically, and you ll be sad. Note that most of the time you don t want to smooth polygons, but for now you can get some practice. d) When you get the result you like, click on Editor -> Save Edits and then Editor -> Stop Editing. Your burn scar shapefile will be complete. Congratulations! You have created your first map unit in ArcGIS. Click File -> Save or the Save button. Note that Editor -> Save Edits saves the things you ve drawn (or data you have entered into an attribute table), but it is not the same thing as File -> Save in the main menu, which saves the map file. IV. SYMBOLOGY Oooh, a big GIS word!! Remember, symbology only refers to how data are represented (symbolized). Symbology ranges from the color and thickness of a line to the size and shape of points to the transparency of a polygon to the contrast and brightness enhancement of a raster image. You will spend a lot of time fussing with symbology. Some people actually spend way too much time fussing with symbology, when they should actually be working on science! 21a) Over in the Layers box of ArcMap, right-click on burnscar and slide down to Properties You will get a Layer Properties window with lots of tabs across the top. Click on the Symbology tab. Because burnscar is a polygon, there will be fill properties and outline properties. Another cool thing about polygons is that you can make them transparent. This is particularly useful for overlaying on bitmaps such as satellite images or shaded relief images. You ll notice a large rectangle with the same color and outline that is displayed in the Layers window on the main page. If you click this button, you will get a Symbol Selector window with all kinds of options for colors, patterns, and outline colors. Select some combination that will be appropriate for a burn scar. It is always useful to select a color that is intuitive, but as noted above you don t have to spend hours making these choices they can be changed at any time. But you might want to not

11 select cyan for the outline color because Arc uses that as an indication of being selected, and it can get confusing. Click OK and then OK again in the Layer Properties window. The symbol for burnscar in the Layers window should reflect the changes you just made. 11 b) To make a polygon transparent, right-click on burnscar again, and in the Layer Properties window, click on the Display tab. Near the top you ll se a Transparent: box that is asking for a percent. Type in 50 and click OK. Unless you want to, there is no need to change the symbology of trackpoint shape files because you are only going to use them as templates for drawing. d) Save the map file: and go on to handout #3.