HW GPS Coordinate Conversions
Background: In the HW, you will convert your GPS UTM coordinates to State Plane Coordinates, and compare
with your field traverse values.
1. In order to compare coordinates, it will be necessary to convert your parcel coordinates to the appropriate
State Plane coordinates. With your UTM coordinates in meters, go to the National Geodetic Survey website
(www.ngs.noaa.gov) and use the online tools to make the conversions to StatePlane. From the homepage, click
on “geodetic tool kit” in the left hand column. On the next screen, click on “Universal Transverse Mercator
Coordinates”. On the next screen, click on “Universal Transverse Mercator Coordinates” (again). You will
now be in a Geodetic Toolkit UTM.
2. Convert your UTM coordinates to Geodetic Coordinates, Lat/Long. Select UTM to Latitude Longitude.
First determine your zone. Most of Florida is in zone 17. Count 6 degree-wide zones from the International
Date Line (180 deg E/W long) toward the east. ZONE1 180-174 W. Long, ZONE2 174-168 W Long, etc,
ZONE17 84-78 W. Long.
Select the NAD83 datum. Enter your MEAN UTM GPS values into this online program and mark down the
deg, min, sec of Latitude and Longitude for each mean GPS UTM coordinate. Enter your original and
converted values into an Excel spreadsheet.
3. Convert your Lat/Long geodetic coordinates to State Plane Coordinates. Go back several screens and select
State Plane Coordinates. Pick the interactive conversions. Lat/Long to State Plane. First find your State Plane
Zone using the tools on the website. For example the University, in Alachua County Florida is in Zone number
903. Click on “Find Zone” under “Interactive Conversions.” Return to this screen and click on “SPC ->
Latitude/Longitude.” On the next screen be sure button “NAD83” is selected and enter your Latitudes and
Longitudes using their format. “Submit.” Copy the X and Y State Plane coordinates for each of your Mean
GPS points. Enter these values into your Excel spreadsheet.
4. Compare values. Prepare a MS Word Doc with complete text discussion of your methods and results. After
giving your methods, answer the following:
A. How do your "traverse" SPC's compare with the converted GPS values?
Make a table of comparison, similar to:
Point
SPC N
Traverse
GPS
Diff
SPC E
Traverse
GPS
Diff
B. Fully discuss the results. Explain whether the comparisons are within expected limits or outside? If
outside, give your analysis of why.
5. Revise your AutoCAD drawing. Create a new point layer "p-GPS" or similar. On this layer, manually enter
your final GPS State Plane Coordinate average values, Navg, Eavg. (one point per lot corner). Label each
GPS point with a label such as "GPS average point location" or similar.
Submit:
1. A MS Word Doc of your lab report you should report the results and also how the accuracy of the GPS
receivers compares with the field measured coordinates. Copy and paste your Excel data files into the Word
document as necessary.
2. Your revised AutoCAD drawing.