Beginning

1
Beginning

• Basic step-by-step demonstration for
• Obtaining Basefile from CORS or local GPS web
  sites
• Using basefiles for Differential Correction of
  Trimble Rover files (.ssf) using Pathfinder
  Office

2
overview
Differential correction compares and corrects
your Rover file using a Base file, from a
stationary base station receiver (at a known
location) for the exact same time as your Rover
file. The first step is to obtain a base file.
The most common source are CORS web sites. Even
though we may not use a CORS site, it is
important to be familiar with the CORS format
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4 CORS home
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5 CORS data
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6 CORS selected
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Use skagit instead
HOWEVER For local GPS work (within Whatcom
County), the Skagit County GPS base station is
supperior Closer 5 second sampling interval
(Whidbey CORS is 30 second) So use
their site instead
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7 skagit cors
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8 skagit ssf
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9 skagit ssf list
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10 skagit ssf select
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11 skagit download
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12 c/pfdata
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13 pfdata/default
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14 File open
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15 zip file
Double click to open
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16 extract
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17 extract to base
Extract to C/Pfdata/default/base folder
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18 base file
Base file in Base folder
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Pathfinder
Now, having downloaded a base file for the
correct time period, a Rover file can be
corrected using Pathfinder office
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1 Windows
Open Pathfinder office
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2 Start Pathfinder
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3 Default
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19 Pathfinder
Add your GPS data
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19 Opened file
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19 open Rover file
Open Uncorrected Rover file in Pathfinder
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19 Opened file
Uncorrected Rover file
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20 Util
Differentially correct your Rover file using the
corresponding base file
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21 diff correction
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wait
Wait for the Differential Correction window to
open for some reason this seems to take a few
minutes.
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22 Local search
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22 Local search in base
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23 matching files
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24 base data ok
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25 smart code ok
Use Smart Code and Carrier Phase Processing
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26 diff cor done
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27 open files
Compare corrected and uncorrected files
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28 Open both files
Open both original Uncorrected rover file And
corrected file for comparison.
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29 zoom
Drag a box with zoom tool
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30 close up of both
Compare the two files
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Export em
Both the uncorrected Rover file and the corrected
file can be exported to ArcView shapefiles for
GIS use and spatial analysis (see
GPS_PF-AV_demo.ppt)
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fini
fini