Lab 3. GIS Data Entry and Editing.

Lab 3. GIS Data Entry and Editing. The goal: To learn about the vector (arc/node) and raster data types entry and editing. Objective: Create vector and raster datasets and visualize them. Software for the lab: ARCINFO, ARCVIEW. Reading: S.Aronoff. Geographic Information Systems:A Management Perspective. Chapter 4-5. NOTES!!!: All ARCINFO commands are in bold. Before you follow instructions, please type them and see the syntax of the whole command. This will help you to understand your action better. After the lab is finished, make sure that you quit the program. Otherwise it will run on the background and slow down the network performance in the lab. IF YOU GET FRUSTRATED or MADE AN ERROR: RADICAL WAY: If you have prompt: Arcplot: then type quit and leave Arcplot:. This will bring you to the prompt Arc: At this prompt type lc. Hit Enter. This command will show you all your coverages. Use command kill <coverage-name> all to get rid of the one that has to be redone. Start all over. SOFT WAY: If you have prompt: Arcplot: then type oops. Watch changes. Oops command will bring you one step back. It is similar to Undo Edits option. You can do it untill you know where are you. Then repeat your commands again. Maybe look at the help menu. Pay attention to various options associated with commands. I. Digitizing From Hardcopies. This lab does not use the digitizing tablet for the data entry. You will use ARCINFO module ARCEDIT that utilizes digitizing tablet as well as a keyboard to enter coordinates of your feature, create its geographical extension, fill with necessary information and store as a raw coverage. Then you will have to use ARCINFO command build to create topology. By the end you will have to add an attribute item. Open Unix command shell. If you do not know what is it, ask system administrator. Create sub-directory in your home directory called lab3 using command mkdir lab3. Move into this directory using command cd lab3. Columbia University, Department of Earth and Environmental Engineering 1

Check yourself by typing command pwd. You should see the last sub-directory name lab3. Now you are ready to start your lab exercise. The first exercise will consist of digitizing a lake from the planimetric image. Planimetric image is a scanned image from the hardcopy map. The name planimetric means that it is a plane i.e. flat and does not have any reference to the curvature of the earth surface. This is very common map product. The image is located in: /usr/manhattan/gis_class/yxg/data/plan56.tif Start ARCINFO software using menue option Arcinfo in Apps toolchest menu (upper left corner of the monitor). Describe the image plan56.tif to find out its extent. You will need to find the minimum and maximum extent of this dataset for the digitizing process. Use ARCINFO command describe. Do not forget that image is in /usr/manhattan/gis_class/yxg/data. Therefore, give the whole path to the image. Record your Xmin,Xmax, Ymin and Ymax values. Start ARCEDIT module by typing the following command: Arc: arcedit Now create a graphic canvas for the display of your future map features: Arcedit: display 9999 You should see the black graphic canvas on your screen. Place it conveniently. Pass control of the coordinates entry to your keyboard via the following command: Arcedit: coordinate keyboard Now create the first dataset that will describe geographical area of your future data - tic marks: Arcedit: create tic56 Enter tic-id numbers that would describe the 4 corners of your future coverage. Take numbers from the output of your command Describe /usr/manhattan/gis_class/yxg/data/plan56.tif in previous step. Calculate the initial boundary as: Xmin - 500, Ymin - 500, Xmax + 500, Ymax + 500. Columbia University, Department of Earth and Environmental Engineering 2

After you finished you should see something similar to the following line: The edit coverage is now /PROJECTS/YURI/TRAINING/EDITING/TIC56 WARNING the Map extent is not defined Defaulting the map extent to the BND of /PROJECTS/YURI/TRAINING/EDITING/TIC56 Save your work by typing at arcedit prompt save. Good luck! Arcedit: save Saving changes for /PROJECTS/YURI/TRAINING/EDITING/TIC56 BND replaced into /PROJECTS/YURI/TRAINING/EDITING/TIC56 This comand saves all your work with data within the ARCEDIT module. Each time you want to draw something within ARCEDIT, you have to specify your drawing environments. Type command drawenvironment and hit Enter button. You will see a lot of options. Now, draw on the canvas the TICs for your future dataset using the following options with the drawenvironment command: environment tic ids (You can also do the shortcut: Arcedit: de tic ids ) You should see on your graphic display the four TIC points that you have entered and their ID numbers. Now let s create the future dataset that will have a geographic extension of the file tic56 that you are already created, using the following command: Arcedit: create lake56 tic56 Creating /PROJECTS/YURI/TRAINING/EDITING/LAKE56 This command created a new dataset called lake56 using geographical extension data from the dataset tic56. Tic56 coverage serves only one purpose - to pass information about the coordinate system of your future data and its units. The edit coverage is now /PROJECTS/YURI/TRAINING/EDITING/LAKE56 Let s draw on the background image file plan56.tif. The following command will do it: Arcedit: image /usr/manhattan/gis_class/yxg/data/plan56.tif transparent 1 You should see the black and white version of the plan56.tif image. If you like different color, change the last option in your command like this (for green) : Columbia University, Department of Earth and Environmental Engineering 3

Arcedit: image /usr/manhattan/gis_class/yxg/data/plan56.tif transparent green Because we do not digitize data from the hardcopy map we are not planning to estimate our RMS error. Our error of digitizing will depend on our zoom to the image. Please find the feature Lake Carmel on the screen. It should be located somewhere north-east from the center of the image. You can use Pan and Extent options om the upper left corner menu of your canvas. The menu is called Pan/Zoom. Let s make sure that our coordinates will be entered via the mouse. To do this type the following: Arcedit: coordinate mouse Now you are ready to create your own dataset with the outline of the Lake Carmel. Specify the features you want to digitize (in this case arcs, since you need an outline) : Arcedit: editfeature arcs (You can do also a shortcut: Arcedit: ed arcs ) You will see the following response: 0 element(s) for edit feature ARCS Coverage has no COGO attributes You have 0 elements because your dataset does not have any features. You have to add them: To make sure that the software enables drawing of arcs type the following: environment arcs (Or use the shortcut Arcedit: de arcs) Let s add them by digitizing the outline of the Carmel Lake. Arcedit: add You will see the following menu: --------------------Options-------------------- 1) Vertex 2) Node 3) Curve 4) Delete vertex 5) Delete arc 6) Spline on/off 7) Square on/off 8) Digitizing Options 9) Quit Remember that you have to start any vector feature with the node. Then you can continue with the vertex and close your digitizing with another node. In case of polygon digitizing your nodes should be digitized at the same location as close to each other as possible. Use numbers on your keyboard to start your node, vertex or delete vertex, etc., corresponding to the numbers from Options above. Columbia University, Department of Earth and Environmental Engineering 4

To digitize Lake Carmel outline from the dataset, start from any place. Just remember its location. You can do digitizing and simultaneously pan your image to digitize at the same resolution. If you will use various Zooms you will not digitize at the same resolution. You can digitize this dataset using only 2 nodes, but if you want to practice, use few nodes. To finish digitizing, hit 9 on your keyboard. To start again, use command add as before. If you make mistake, hit 9 key and type at Arcedit prompt command oops. When finish digitizing, save your dataset using command save. You will see the following: Arcedit: save Saving changes for /PROJECTS/YURI/TRAINING/EDITING/ROAD56 Saving arcs... 2 arc(s) written to /PROJECTS/YURI/TRAINING/EDITING/ROAD56 from the original 0, 2 added and 0 deleted Reopening arcs... Saving tics... ** NOTE ** Tic(s) unchanged Reopening tics... BND replaced into /PROJECTS/YURI/TRAINING/EDITING/ROAD56 Re-establishing edit feature ARC Coverage has no COGO attributes Now, remove your image (in real world you would remove the hardcopy map from the digitizing tablet) using commands: Arcedit: image off You will see only outline of the lake. Let s check if you have any dangle nodes. The following command set your software to display all nodes: environment node dangle Let s assign to the dangle node red color for better visualization: Arcedit: nodecolor dangle red Now, redraw your data: Look at the screen! Any red color nodes? If the answer is no you are lucky!!! and let me know about it. Last year (1999) only one student digitized that precisely and did not have any dangling Columbia University, Department of Earth and Environmental Engineering 5

nodes. Otherwise you should see the red colored square where you nodes are hanging. Zoom in really close. See the gap between two nodes? Now it is time to correct this error. Use the command nodesnap to set up the threshold values for your editing. You will have to specify the radius within which your editing will work. The following command basically means: I want my nodes being snapped within the distance that I will define using a circle, and any first node within this distance should be snapped (i.e. connected). Arcedit: nodesnap first * Define the tolerance circle Enter the center Enter the edge Now change your editing mode from arcs to node : Arcedit: editf node Use ARCEDIT command move to connect (or snap ) your nodes together. When prompted, click on the node, then hit the keyboard number 4 (move) and then select the second node with your mouse pointer. You should see how node will be moved and conncted with another one. Instead of the red square you will see white romb. This means that your nodes snapped succesfully and instead of dangling nodes you created pseudo-node. Arcedit: move Point to the node to move <9 to Quit> Enter point Node (610944.812,4589545.000) selected 1 = Select 2 = Next 3 = Who 4 = Move 9 = Quit Save your work using command Save. Remove image from the background using command image off : Arcedit: image off Redraw your graphics: Now you should see the black canvas and the white outline of the Carmel Lake. As you can see it is just outline. Now we have to add a label point to this dataset. Columbia University, Department of Earth and Environmental Engineering 6

To do this, change editing mode in the software to start editing/adding label points (remember, we are dealing with the polygon!). Use the following commands: Arcedit: editf label 0 element(s) for edit feature LABEL You have 0 elements because you do not have labels yet. Add the label for the polygon using the following command: Arcedit: add --------------------Options-------------------- 1) Add Label 5) Delete last label 8) Digitizing Options 9) Quit Place your mouse pointer in the middle of the Lake Carmel and hit key 1 on your keyboard or click with the left button of the mouse. You will see yellow cross mark appearing on the screen. Hit 9 key on your keyboard to stop the editing process. Now you have a typical polygon dataset within an arc/node structure. While you are in a label editing mode you can view the attribute table of your newly created node using command list : Arcedit: list Record 1 As you can see the label has only one attribute - ID# = 1. It does not have any other attributes because we have not build our topology yet and the software does not know what kind of attribute table to use i.e. point, line or polygon. To build topology we have to quit ARCEDIT module using the following command: Arcedit: quit Keep all edit changes (Y/N) : y This will replace all changes back into the original coverage(s) and/or INFO file(s) Do you really want to do this (Y/N) : y Saving changes for /PROJECTS/YURI/TRAINING/EDITING/ROAD56 Saving arcs... ** NOTE ** Arc(s) unchanged Saving labels... ** NOTE ** Label(s) unchanged Saving tics... ** NOTE ** Tic(s) unchanged BND replaced into /PROJECTS/YURI/TRAINING/EDITING/ROAD56 Columbia University, Department of Earth and Environmental Engineering 7

Saving set tolerances to TOL file... Leaving ARCEDIT... Arc: Now you are back to the ARC module. ARC module is familiar to you from the previous lab. Use command lc to view your newly created coverage lake56. Arc: lc Workspace: /PROJECTS/YURI/TRAINING/EDITING Available Coverages ------------------- LAKE56 TIC56 Arc: You should see in your workspace two coverages: lake56 and tic56. Now build topology: Arc: build lake56 poly Building polygons... Let s list the attribute table using the following command: Arc: list lake56.pat How do we call this file? What does it store? Send me e-mail. You should see such attributes as lake56# and ID#, Area and Perimeter. These are automatically created attributes that software produces for you as soon as you build topology. In case of lines you would see Length, etc. Now you should have your lake56 coverage set as a polygon coverage with appropriate label. Next step will be attribute table update. You can do this from ARC module using command additem : Arc: additem Usage: ADDITEM <in_info_file> <out_info_file> <item_name> <item_width> <output_width> <item_type> {decimal_places} {start_item} In our case we ll issue command with the following options: Arc: additem lake56.pat lake56.pat name 30 30 C Adding name to lake56.pat to produce lake56.pat. Arc: Columbia University, Department of Earth and Environmental Engineering 8

This command added an item (feature attribute) called name having width of 30 characters. Capital letter C means that the item is set up as a character based. Other options might include integer or floating numbers with various decimal places. Let s list the attribute table using the following command: Arc: list lake56.pat You will see regular attributes such as AREA, ID#, etc., and also your own attribute NAME that will have a blank line next to it. This is because we have not assign a value to this attribute. Let s assign value Lake Carmel to it. We ll do this in our next Lab4 after closer look at the attribute table editing. Make a list of all commands you used and classify them into two categories: 1. Management of graphic elements and computer settings. 2. GIS database construction. Send me e-mail with all answers. Columbia University, Department of Earth and Environmental Engineering 9

II. Survey data entry in GIS. Survey data are usually flat files that store geographical information and description of the feature that was surveyed. Survey can be done using automated data collection, such as Global Positioning System or manual - theodolite, line, etc. For this exercise use ARCVIEW software. We will have to import a flat file that was created by surveying USGS gauge stations (remember Lab2!) into ARCVIEW. You are given this file and asked to create a GIS dataset. Close any other software you use. Start ARCVIEW (look in Apps upper left corner of the monitor). Save your project as lab3.apr. Open new View. Set up your View properties as following: Call the view USGS Monitoring Sites. Map Units - meters. Distance Units - meters. Click on the icon Tables within your project window. Using Add button add a table usgs.txt from: /usr/manhattan/gis_class/data View it. As you can see this table has three columns: X,Y,Site. X,Y fields store coordinates, while Site has unique identification number for each USGS monitoring gauge. Make your view USGS Monitoring Sites active and add the table usgs.txt to the view using the sequence of menues: View ---> Add Event Theme. Select table usgs.txt. You should see that X field has X value and Y field has Y value. This happened because fields in the table were named as X and Y. If you would have more complex table, you would be able to select the fields storing X and Y coordinates yourself. Click OK button and you will see how in your view USGS Monitoring Sites a new theme appeared with the name usgs.txt. Make it visible and assign the red filled circle as a symbol. Save this project and send me e-mail that you finished. Columbia University, Department of Earth and Environmental Engineering 10