Texas Ecosystem Map - GIS and Mapping - Lecture Notes, Study notes of Geology

Download Texas Ecosystem Map - GIS and Mapping - Lecture Notes and more Study notes Geology in PDF only on Docsity! ”Purveying Global Information for the Global Economy” Texas Ecosystem Map Well, I hear that despite some frustration you can now know competently perform map projections and transform geographic themes into an appropriate map projection. Congratulations these are fundamental GIS skills that you will continue to use (at least while you are working at Aggieland Geomatics ☺). You now have a new task. Aggieland Geomatics has just won a contract to examine Texas’s state parks system in reference to how well Texas’s parks are distributed across its major ecological zones. The state wishes to determine if it needs to add some parks to give its populace better access to certain aspects of the diverse landscapes of this great state. Unfortunately we have been unable to locate a digital version of the Texas Ecological Region map for our GIS so we will need you to digitize the Ecoregions of Texas from this map we obtained from the Perry-Castañeda Library Map Collection at the University of Texas ( ). In addition to simply digitizing the coverage, I would like you to add two attributes fields to each polygon you construct. The first attribute field should be an integer field containing the ecosystem number from the map and the second attribute field should be a text field with enough characters to hold each ecosystem name. Because we need to compare the areas of the different Texas ecological regions compared to the number of state parks found in each please permanently reproject all data into an appropriate Texas Centric projection. Map projections commonly used by state agencies can be found at . I would you to provide to your supervisor the following things: 1) A written memo with a one to two page description of how you compiled your ecosystems map as well as any problems/issues you may have encountered in its construction, and 2) A screen snapshot of your table preview of your completed file from ArcCatalog, and 3) A printed color 11” wide by 8.5 high map of Texas showing its ecoregions with respect to named parks. The map should have a complete and intelligible legend. Good luck! Docsity.com Detailed Instructions 1) Basic Instructions A. Before beginning the lab…read the instructions carefully and note that these instructions are not necessarily in the order in which the steps may best be accomplished. B. Copy the directory lab09:\student_data to an appropriate place in your home directory. It has most of the files you need to successfully accomplish this lab. 2) Projecting GIS coverages A. All the coverages provided in the student_data directory have the correct projection information already defined so it is not necessary to use project define B. Select the appropriate projection carefully given what is requested in the directions. C. Save the new files as Shapefiles (it is the easiest approach) 3) Rectifying the texas_ecosystems.gif file. I would approach the georeferencing as follows. A. In ArcMap add the Texas counties theme B. Adjust the data frame properties to set an appropriate Texas map projection for the task at hand. C. Georeference the image to this “on-the-fly” projected theme of Texas county outlines using the skills you gained in the last lab. I was not able to achieve a perfect fit between the image and the projected county outlines. However using approximately 15-20 tie points and a 2nd order polynomial warp I was able to achieve a satisfactory fit. D. Rectify the image and save the resulting file as an ARC/INFO Grid with 1000 meter resolutions. By saving it as a grid, it should attach the correct projection information to the rectified grid, but after you have saved the grid make sure that the projection is properly defined. 4) Creating and Digitizing the Texas Ecosystems A. Using ArcCatalog create a new Shapefile containing polygons to hold your digitized ecoregions. In order to assure that your created ecoregions will have the correct projection information, you should Edit the Spatial Reference information and Import the projection information from your transformed raster image. B. Remember to define the two attribute fields that you will populate once you create the feature geometry. This also is easily done in ArcCatalog by simply editing the properties of the shapefile you have created. This should be done before you begin digitizing. An example is shown in the figure below. Docsity.com