Exporting GPS to GIS Format

Discussion

The next step in a GPS project is to export your collected data files to a format compatible with your organization's GIS database. Formats may include, but are not limited to shapefile, coverage, geodatabase feature class, and AutoCAD. This section identifies GPS configuration options, processing software for GPS unit types and provides links that walk you through the export process.

Deciding on the right GPS unit and processing software from the start will dictate how many options you have in configuring exports. READ MORE >>

Capability to export to different formats allows you maximum flexibility in handing data to various agencies or other software platforms. GPS processing software varies based on the type of GPS unit you are using. See the GPS Unit & Project Needs Assessment step for more details on GPS units.

Exporting GPS data in the correct projection and datum is the most important component of any Export function. READ MORE >>

The export software should have the capability to output in the spatial coordinate projection and datum of your GIS. Since the removal of Selective Availability recreational grade GPS units have been used more for GIS mapping purposes. Keep in mind that errors from these units are introduced when using an inadequate or non-robust projection/datum transform engine. Third party software may rely on less robust datum transformations (from WGS84 - NAD27). See the Watch Outs and Links section to learn more about datum transformations.

Mapping Grade GPS receivers allow additional information, called generated attributes (values such as PDOP, correction type etc) to be transferred with the GIS data. READ MORE >>

These attributes will be stored in attribute tables alongside user defined attributes recorded during feature collection. Exporting these attributes assist in describing horizontal and vertical accuracy for the data quality section in FGDC metadata. See the Data & Process Documentation step to learn more about metadata.

Watch outs!

Check the units - Be sure to verify the units of your features, such as distance and area, are compliant with your GIS. If any edits are applied to your GPS exported features AFTER export, you must update these units in the attribute table.

Projections and Datums - Check with your park or regional office GIS staff to ensure the correct projection and datum is used for the GPS data. It is especially important that if you require NAD27 Datum coordinates that you use NADCON Grid Datum transformers. When using Pathfinder Office, you must select the NADCON (Conus) if you are in conterminous US, or NADCON (Hawaii or Alaska) when appropriate. This conversion is the federally accepted datum conversion program. The Links section provides software transformers for recreational\consumer grade GPS units.

Set Projection in DNR Garmin - Setting the projection before you transfer the Garmin data into ArcView ensures data compatibility with your GIS.  All data transferred from the Garmin is in Latitude/Longitude, Decimal Degrees, WGS84 Datum. You can choose to use the data in this format or you can have ArcView automatically convert the data to any projection it supports. Use the menu choice DNR Garmin | Set Projection to set that projection.

Take the NAD83 Leap of Faith - Recreational\Consumer Grade unit users, to retain the greatest accuracy of a GPS position, taking a raw WGS84 coordinate from a GPS is better. Translate the WGS84 coordinate to NAD27 within a robust program (ie. ArcINFO, ArcView, or Corpscon) by "lying to" the program that the incoming coordinate is NAD83 and then use a NADCON translation to NAD27.  The difference between WGS84 and NAD83 is inconsequential with mapping grade GPS. (See link http://gpsinformation.net/main/dgpsdatum.htm).

Use projection files - Most GIS software behave well when given information on the projection and datum of a GIS theme. When using ESRI software, this information is stored in a projection file (extension *.prj). If your software reads/writes a GIS dataset, check the projection parameters to ensure compatibility with your GIS. If the software does not produce a projection file, you can store these in a local folder and copy them alongside the dataset. BE CAREFUL when using this method! You should be 100% sure when assuming a coordinate system and or datum of a dataset. See an example of a PRJ file.

Glossary of Terms

AutoCAD - An AutoDesk file format for large scale technical vector data. This format stores very little attribute information per feature and point, line and polygons are represented.

Coverage - An ESRI GIS vector data file. Fairly common among ArcInfo users. The data file is more complex, representing point, lines, and polygons features and relationships between features.

Geodatabase - An ESRI GIS vector & raster data storage file system. New for ArcGIS 8.x users. The data file system is the most complex ESRI file format representing many feature types and complex relationships between features. The geodatabase can reside locally on a PC or be stored in a multi-user database such as Oracle.

Selective Availability - The deliberate introduction of error to the precise timekeeping of the GPS satellites. This technique degrades both positioning and timing accuracy for civilian users.

Shapefile - An ESRI GIS vector data file. Fairly common among ArcView 3.x users and third party GIS software packages. The data file is simple, representing point, line, or polygon features.

Links (Step-by-Step How To)

• NPS Alaska Support Office on DATUM Transforms [MS Word Document] (43 Kb) - Datum Transforms for GPS data between WGS84 and NAD27 [December 2003]
• Independent website link on the difference between WGS84 and NAD83 - http://gpsinformation.net/main/dgpsdatum.htm [unknown]

• US Forest Service Comparison of 3rd party software for Garmins [MS Word Document] (630 Kb) - Garmin GPS Data Processing Software Comparison [2003]
• NPS Washington Support Office information Link (7 Kb) - Data Collection, Exporting and Importing [vintage unknown]
• Minnesota Depart. of Natural Resources Web site with the a Utility for data transfer between Garmin & ArcView 3.x - DNR Garmin Extension for ArcView 3.x [2004]
• NPS Alaska Support Office on Installing DNR Garmin (81 Kb) - Installing Garmin Data into ArcView 3.x [April 2004]
• NPS Alaska Support Office coarse materials from "GPS for Ologists" [Adobe PDF] (~2.7 Mb) - Tutorial on Garmin Data and ArcView 3.x [Summer 2004]
• Interagency "GPS for Fire Management" coarse material [Adobe PDF] (609 Kb) - DNR Garmin: Track Management for Multiple Tracks [2004]
• Interagency "GPS for Fire Management" coarse material [Adobe PDF] (363 Kb) - Loading the DNR Garmin Extension in ArcView 3.x [2004]
• Interagency "GPS for Fire Management" coarse material [Adobe PDF] (512 Kb) - DNR Garmin and ArcView: Waypoint and Track Download [2004]
• Interagency "GPS for Fire Management" coarse material [Adobe PDF] (308 Kb) - DNR Garmin and ArcView: Waypoint and Track Download...Continued [2004]
• Owen Earley at Waymex IT posted an ESRI ArcMap Toolbar GPSi for Garmin to ArcGIS - GPSi (GPS Interface) [February 2004]
• Alan Murphy's stand alone GPS Utility for GPS data transfer, management, manipulation, and mapping - GPS Utility [May 2004]
• ESRI GPS Utility Toolbar for data transfer between most GPS receivers and ArcGIS 8.x - ArcMap GPS Support (ver 8.x) [2003]

• NPS Alaska Support Office on Pathfinder Office and ArcView datum transformation [MS Word Document] (179 Kb) - Datums [2002]
• NPS Alaska Support Office on ArcPad and NAD27 [MS Word Document] (24 Kb) - Use of ArcPad in a NAD27 World [December 2003]
• NPS Alaska Support Office document on Pathfinder Office export tips [MS Word Document] (85 Kb) - Miscellaneous Tips [2002]
• NPS Alaska Support Office document on Pathfinder Office exports to Arc/Info coverage format [MS Word Document] (55 Kb) - Pathfinder Office to ArcINFO [2002]
• NPS Northeast Support Office on Pathfinder Office Suggested Export Settings [MS Word Document] (22 Kb) -GIS Data Export Settings [2002]
• NPS Colorado National Monument's guide to Trimble Pathfinder Office [MS Word Document] (528 Kb) - COLM GPS Project Methods [Summer 2002]
• NPS Zion National Park on exporting from Pathfinder Office software [MS Word Document] (104 Kb) - Export Setup Properties for Arc/Info Unix [November 2003]
• US Forest Service, Coconino National Forest document with a warning about Polygon Export to Arc Generate Format [MS Word Document] (310 Kb) - Issue with Polygon Export to Arc Generate [2004]
• US Forest Service, Gila National Forest on exporting from Pathfinder Office [Adobe PDF] (237 Kb) - Exporting GPS Features to Arc/Info Coverages [2000]
• Unknown authorship guide listing GPS export settings parameters in Pathfinder Office important for metadata [MS Word Document] (21 Kb) - Metadata from GPS Field Work [unknown]

• NPS Alaska Support Office on datum conversion with the Projection Utility Wizard [MS Word Document] (~1 Mb) - Projecting GPS Data [2002]
• See also the links in the Recreation\Consumer Grade GPS Receiver Users section above

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