Adding GPS Data

1
Adding GPS Data

• John Q. Murray
• Murray Information Services, Inc.
• johnnyq_at_murrayinfo.com

2
Many different ways

• Take readings on a GPS unit, write them down on
  paper, enter into the desktop PC
• Transfer directly from GPS to the desktop
• Obtain GPS files from others (email, disk) and
  bring them into the desktop PC

3
Recording GPS values by hand

• Record GPS values from the handheld unit onto
  paper and enter them into the computer later
• ArcView wants lat / lon in a particular format
• Decimal degrees
• West longitude as a negative number

4
Turn it into an ArcView theme

• Open the .txt file as a table
• Add an event theme
• View -gt Add event theme
• Select the decimal degrees longitude as the x
  field
• Select the decimal degrees latitude as the y
  field
• Use Projection Utility as needed to match other
  themes

5
Adding from .COR files

• Common interchange format for GPS data .COR
  (corrected) files
• Need to convert these files using desktop
  software that comes with the GPS
• Trimble provides a suite called Pathfinder Office
• For example, 3 .COR files from EPA Superior Iron
  Mountain mine sampling project
• R101814.cor, R101616.cor, R101714.cor

6
ID associated with each point

• IM represents the project (Iron Mountain)
• SO soil or source sample
• GW groundwater samples
• SW surface water
• SE sediment sample
• Number values are consecutive based on the type
  of sample (surface water, groundwater)

7
Convert to shapefiles using Trimble Pathfinder
Office

• Open the data files
• Export them as ArcView files
• Then use an ArcView script to merge the 3 themes
  into 1 call the new single theme epadata.shp

8
Tool to merge themes

• Handy little script from the ArcView helpfile
  MergesActiveThemes

Combine 3 point themes into one epapoint.shp
9
Project the EPA data

• Use the Projection Utility to match the EPA data
  with other themes
• One interesting new step a datum conversion
• Select the Datum tab
• Choose the geographic transformation from WGS
  1984 to NAD 1983

10
EPA sample locations, Superior
11
EPA sample locations, Flat Creek
IM Iron Mountain SO soil or source GW
groundwater SW surface water SE sediment
BOB lines representing the width of the
tailings piles