Spatial Analysis Lab (SAL)

How to get POINT Data from a

(Trimble GeoExplorer 3) GPS Line Feature
(Can be used as a Method of Obtaining a Series of Points at a Set Interval)

 

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One of the missing features on the GeoExplorer 3 GPS receivers is that there is not a direct way to record a point feature every X seconds. The workaround for this shortcoming is to record a line feature (setting the recording time interval to X, as desired) and then export the �positions� (or vertices) of the line as multiple points rather than exporting the line as one linear feature. Details on both the recording and exporting steps are below.

 

 

To Record a Line with Positional Readings at a Set Interval

  • Turn the GeoExplorer 3 unit on (should open to the Skyplot screen)
  • Press the System button twice to go to the System / Setup screen
  • Highlight Feature Settings and press the Enter button
  • Highlight Generic (or the data dictionary of your choice) and press Enter
  • Highlight Line and press Enter
  • Highlight Interval and press Enter
  • On the Interval screen:

                  Make sure the Time radio button is selected

                  Use the right/left arrow buttons to select a units column

                  Use the up/down arrow buttons to change interval

  • Press the Close button to close the Interval screen
  • Press the Close button to close the Line Setting screen
  • Press the Close button to close the Edit Feature Settings screen
  • Press the Close button to close the Select Feature Settings screen
  • Press the System button to return to the Skyplot screen

 

 

NOTES:

The GeoExplorer 3 will now record a position every X seconds any time you are capturing a line feature. These positions, by default, are connected into a single line feature, but can be obtained separately by following the steps below.

 

Multiple line features can be recorded as usual, as well as other features (points or polygons).

 

If you wish to have some lines as lines (perhaps with a different recording interval) and some that will later become positional points, use separate data dictionaries to set different recording intervals and switch between data dictionaries and rover files as needed in the field.

 

 

To Export the Point Positions of a Line Feature

  • Turn the GeoExplorer 3 unit off
  • Place the GeoExplorer 3 unit on a transfer cradle connected to the computer
  • Open Pathfinder Office
  • From the Utilities menu, choose Data Transfer� to download the data (rover files with a .ssf extension) from the GeoExplorer 3 to the C:\Pfdata folder
  • From the File menu, choose Open and browse to your transferred .ssf line file(s)
  • From the Utilities menu choose Export
  • In the Export dialog box:

                  Make sure your .ssf file is in the Selected Files box

                  Under Choose an Export Setup,

                        choose Sample ArcView Shapefile Setup

                  Click on the Properties button

  • In the Export Setup Properties dialog box:

                  Click on the Data tab

                              Click the radio button next to Positions Only

                              Make sure the drop down box says �One point per GPS position�

                  Click on the Attributes tab

                              Under All Feature Types, click Date Recorded and Time Recorded

                              Under Point Features, click Position

                  Click on the Position Filter tab

                              Click Uncorrected (unless you have done a differential correction)

                  Click on the Coordinate System tab

                              Optional: Click Use Export Coordinate System

                                          Click Change�

                                          Choose a coordinate system. Recommended options:

                                                      UTM, zone 10 N, NAD 1927 (Western US)

                                                      US State Plane 1927, WA North, 4601

                  Click OK to close the Export Set Properties dialog box

  • Click OK to export your .ssf line file to an ArcView points shapefile
  • Close Pathfinder Office
  • To view your data in a GIS:

                  Open your GIS software

                  Add data and browse to your C:/Pfdata/<project>/export folder

                  Select the PosnPnt.shp file to add

  • To view your data in Excel

                  NOTE: opening and editing a shapefile in excel can cause it to no longer

                              function as a GIS shapefile� make a copy first if you wish to also

                              use this file in a GIS as a shapefile.

                  Open Excel

                  From the File menu choose Open

                  In the Open dialog box, change Files of type to All Files (*.*)

                  Browse to your C:/Pfdata/<project_name>/export folder

                  Open PosnPnt.dbf

                  Note: This can be saved as an excel file or exported to a text file if desired

 

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