tools of the trade l.
Skip this Video
Loading SlideShow in 5 Seconds..
Tools of the Trade PowerPoint Presentation
Download Presentation
Tools of the Trade

Loading in 2 Seconds...

play fullscreen
1 / 28

Tools of the Trade - PowerPoint PPT Presentation

  • Uploaded on

GPS Communication Software. Mapping Program. Tarpits and Tips. Tools of the Trade . GPS. Tools of the Trade - Part IV. Tarpits and Tips. TIPS. Outline. Datums Error, Accuracy, and Precision Map Scale and Errors Tips for Managing GPS Error Better Maps for GPS. GPS Datum Tarpit.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

Tools of the Trade

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
tools of the trade

GPS CommunicationSoftware

Mapping Program

Tarpits and Tips

Tools of the Trade


tools of the trade part iv
Tools of the Trade - Part IV

Tarpits and Tips


  • Datums
  • Error, Accuracy, and Precision
  • Map Scale and Errors
  • Tips for Managing GPS Error
  • Better Maps for GPS
gps datum tarpit
GPS Datum Tarpit
  • What’s the big deal?
    • A football field of difference if you are wrong!
    • What if you’re on the wrong side of the ridge?
    • Or worse…the valley!!


when datums matter
In the Field

Comms between GPS users

Comms between GPS and Maps

Example: dispatch in one datum, you read off in another

In the GIS

Projecting data on top of GIS data

Example: You set DNRGarmin Projection to UTM 10 NAD83, but your GIS is in UTM 10 NAD27

When Datums Matter


or Spoken




400 feet off

Display set to NAD27

They Expect WGS84


Transfer to


Set Projection in DNR Garmin to NAD27



Always Stores in WGS84

Working in NAD27

gps datum tips
GPS Datum Tips
  • Summary:
    • Check, check, check
    • When Downloading with DNR Garmin, Always check “Set Projection” to match your GIS
    • ASK!
    • When you hear WGS84, with your scale, it’s the same as NAD83

Aviation GPS is always WGS84

error accuracy and precision
Error, Accuracy, and Precision
  • Importance
    • Safety
    • Make or break a GIS project
  • Learn ways to keep GPS errors to a minimum
  • Be aware of the issues

Kenneth E. Foote and Donald J. Huebner, The Geographer's Craft Project, Department of Geography, The University of Colorado at Boulder.

basic definitions
Basic Definitions

1.) Accuracy: how close to truth or accepted values.

2) Precision: how repeatable or consistent

basic definitions13
Basic Definitions

Accurate + Precise

= Low Error !

3.) Error: includes both the imprecision of data and its inaccuracies

map scale
Map Scale
  • Accuracy and Precision for a map are a function of the scale at which the map was created
  • Applies for digital or paper
  • National Mapping Accuracy Standards employed by USGS
map accuracy standards
Map Accuracy Standards
  • 1:2,400 ± 6.67 feet
  • 1:24,000 ± 40.00 feet
  • 1:63,360 ± 105.60 feet
  • 1:100,000 ± 166.67 feet
map scale and the garmin
Map Scale and the Garmin
  • Will your Garmin GPS MAP76 meet Mapping Accuracy standards for a 1:24,000 scale product (+/- 40’)?
  • How about 1:63,360 (+/-105’)?
  • Yesterday, we answered that question?
sources of map errors
Sources of Map Errors
  • Age of Data
  • Map Scale

Mapsource data is 1:100,000 scale

  • Digitizing Errors
tips for managing gps error
Tips for Managing GPS Error
  • Metadata
  • Average all Points
  • Fresh batteries
  • External Antenna
  • All else fails
    • Map and Compass
tips for managing error
Tips for Managing Error
  • Staying As Accurate as possible

+/-26 ' (open)

tips for managing gps error20
Tips for Managing GPS Error
  • Record Metadata:
    • Who, What, Why
managing gps error
Managing GPS Error
  • Try to average points
  • 60 points
managing gps error22
Managing GPS Error
  • If in the trees, turn off WAAS
  • Position can be even worse.
  • Always take a 3D position over a 2D Differential!
managing gps error23
Managing GPS Error
  • Try to use Antenna when possible
  • A Map76 under Canopy gets twice as accurate with an external antenna
  • Use Sleeve mounts if you have to
  • When mounting in vehicle, use brackets
gps accessories
GPS Accessories
  • Maps
  • Compass
  • GOTO:
    • Distance
    • Bearing
ideal gps accessories
Ideal GPS Accessories
  • Extra AA batteries
  • Case ($14.00)*

holds cables,




make great maps
Make Great Maps
  • Practice Collecting Good Data in the field
  • Pass onto others only important stuff
  • Make your data secure
  • Importance of Datums
  • How error free are you?
  • By managing error you can beat the odds