Difference between revisions of "Trash-talk"

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(Importing Data Files)
(Reprojecting vector maps)
Line 76: Line 76:
*Hit '''Run'''
*Hit '''Run'''
*The point map should now be in the same location as the county map and with the same coordinate system, meaning the two can be displayed together
*The point map should now be in the same location as the county map and with the same coordinate system, meaning the two can be displayed together
*This process can be repeated for all point maps

Revision as of 11:32, 23 July 2009

Managing Data Files

This section covers how to download the data from the GPS unit, convert it to the necessary file type, and ultimately integrate it into GRASS.

Downloading Data Files

  • Connect Scout Unit to computer using Serial to USB and USB cables
  • Open the Protrak SCOUT software
  • Select appropriate unit
  • Select Download History Log
  • Follow the on-screen instructions
  • Once the download is complete, repeat the process for all units
  • The data will be stored as GPS files in the following directory:
C:\Program Files\PROTRAK\Data
  • From here, the data can be copied to a separate folder for backup purposes

Converting Data Files

  • Open a web browser to the following page:
GPS Visualizer
  • Select the Convert to Plain Text option
  • Select Choose File and browse the directory to find your desired file
  • Under Plain Text Delimiter, select pipe (|)
  • Under Plain Text Output Units, select U.S.
  • In the Time offset: field, type -4
  • Select the Convert button near the top

You should be redirected to a page with a text box that has the data in text format. Near the top of the page you will see a link with a string of numbers ending in .txt

  • Right-click on the link and select Save Linked File As...
  • Choose a descriptive name for your data and change the ending to .csv, essentially saving it as a CSV file

Importing Data Files

Creating a new GRASS location

  • Launch GRASS
  • On the right-hand side select Location Wizard under Define new location
  • Leave the GIS Data Directory field as is but choose a descriptive name for the Project Location
  • Continue to the next page
  • Choose Select Coordinate System and continue
  • Type in ll for the Projection Code or scroll down the page to find Lat/Lon
  • Continue to the next page
  • Choose Select Ellipsoid
  • Type in wgs84 or scroll down to find it at the end of the page, its the very last entry
  • Continue to the last page and select Finish
  • You can set the default extent for the region but it can also be left alone for now

The location that we will use to import the .csv files is now set up with the appropriate coordinate system. This will allow us to validate the points' relative locations to each other.

Importing .csv files

  • Select the location created using the lat/lon projection under Project Location and hit Start GRASS
  • The python GUI should start
  • Under the File menu choose Import vector map which produces another menu, select ASCII points/GRASS ASCII vector import
  • Select Browse and choose any of the .csv files that were just recently made
  • Below that name give the output vector map a suitable name
  • Under the Columns tab designate which column gives the longitude and which one gives the latitude
  • Under the Optional tab, choose to skip the header row by giving the number of header rows that will be skipped, in this case its 1
  • Hit the Run button
  • A vector map with the point data from the .csv file should have been created that you can now display by selecting the Add vector map layer button in the GRASS GIS layer manager window
  • You will have to right-click on the layer and select Zoom to selected map because we did not set the default extent for the region, so it will not show by default (does not apply if you did set the default extent)

Creating location using preferred coordinate system

The Richmond Sanitary District has provided a map of the county using the Transverse Mercator projection. Unfortunately, we cannot just overlay the point map of our data with the map of the county without doing some coordinate system conversion. Luckily, this feature is built into GRASS and we will take advantage of this but first we have to import that map into GRASS to use as our basemap.

  • Relaunch GRASS and select any starting location to start GRASS
  • Under the File menu, choose Import vector map, then Import vector data using OGR
  • For the OGR datasource name: field, select Browse and choose the Parcel_BND.shp file
  • Below this, choose a descriptive name for the output map
  • Under the Optional tab name the location that will house the imported county map, which will be created once the Run button is selected
Note: This will be used as the location for all subsequent point map reprojections
  • The command will take almost two minutes to process but will be set up with the preferred coordinate system for later use
  • We are now ready to begin importing the .csv files that contain the data for the point maps

Reprojecting vector maps

  • Using this location, we can import the point maps and overlay them onto the county map
  • Under the Vector menu, select Develop vector map, then Reproject vector map
  • Give the location of the desired point map in the Location... field
  • Give the name of the input vector map under the Optional tab as well as a different name for the output vector map (if desired, otherwise the name will stay the same if this field is left blank)
  • Hit Run
  • The point map should now be in the same location as the county map and with the same coordinate system, meaning the two can be displayed together
  • This process can be repeated for all point maps