GPS Surveying ©2010 Dr. B. C. Paul Note – The techniques shown in these slides are considered common knowledge to surveyors. Figures in the slides may be the authors own work or extracted from Instrument Users Manuals, Surveying by Bouchard, Mine Surveying, or various internet image sources.

What is GPS GPS computes your position from known satellite locations

What is Being Done With GPS You can go to points in the field – key information in on a key pad and it will radio data back and draw your points in on a base map –(of course this costs about $150,000 to $450,000) You can put GPS on a bulldozer blade and the GPS will guide the blade without laying out grade –Great promise for reducing highway costs and speeding construction

More Uses It can guide driverless truck systems at mines It can track shovel dippers through material being dug – compare that to maps predicting grade and tell the operator shovel by shovel what is ore and waste It can also be used for recreation, and guiding autos

Why this Class does not Follow the GPS Revolution Much We are geared toward training underground surveyors Satellite signals do not penetrate underground We need to use conventional surveying control underground –Thus this class emphasizes conventional techniques throughout

Our Simple Field Lab (#2) We will use recreational grade GPS equipment (accurate to about 20 feet) You will go to each of your surveying points where you set up equipment –(see why keeping your stakes is important) –This does not include building corners that you did as side shots. You will get the coordinates and plot these point locations on your final map as a check on your traverse survey.

A Problem with Your GPS Coordinates They are in latitude and longitude Remember in Plane Surveying we treat the world as a flat Cartesian Coordinate Plane –How do you make Plane surveying in local areas match up with large area survey work which must consider that the world is more of a deformed sphere

The State Plane Coordinate System A grid of points from a deformed sphere projected onto flat planes Math can get ugly (we won’t deal with it) –We will use a computer program to convert our latitudes and longitudes into State Plane Coordinates –Our point locations and directions have been State Plane Coordinates.

Activate Franson Coord Trans

The Intro Screen Comes Up The program works By putting Coordinates in One system on One side Saying what you Want the Coordinates to be In on the other side And then left clicking An arrow (the calculations Can be involved But the software Does the work).

Lets Consider What We Have We have a whole bunch Of latitudes and longitudes In degrees minutes and Seconds. W We thus left click the radio Button to indicate we have Latitudes and longitudes We also click the radio button To indicate we are in Degrees Minutes and Seconds (DMS)

Next We Consider the “Datum” Real points on the earths surface are located in all sorts of ups and downs For map purposes we project those points onto a smooth surface –State plane coordinates are projected onto a flat plane buried in the earth –GPS Coordinates are projected onto the surface of an ellipsoid The default ellipsoid for most GPS units is an ellipsoid that trys to fit the whole world –It is called WSG84 (the 84 part means it was standardized in 1984)

Left Click on the Little Dot Box to see a list of options for the Datum

On the left Side of the Screen We Pick What We Were Trying to Fit Most hand Held GPS Units try to Fit the whole Earth since They are Sold world Wide and Could be Opened up Anywhere We left click On earth (actually it Was already The default)

Then We Look Down the Right Side for a Datum We Like that was made to fit the earth It turns out that WSG84 is one of The options so We highlight and Left click it (actually this too Was the default) Then we left click Ok.

Next We Consider Whether Our Latitudes and Longitudes are North, East or What? We probably Waste little time Figuring we were In the Northern Hemisphere So we pick North as the type Of latitude we Have.

Longitude is Measured East and West of the Greenwich Meridian The Greenwich Meridian runs Through England And we in North America Are definitely West of that So we pick west For our Longitude.

Now Lets Work the Right Side and Figure Out What We Want for Output Since we want State Plane Coordinates we know we Want things in Eastings And Northings. We better pick what we want Our units in because I have A feeling that meters is not “our cup of tea” Left click the arrow to pull Down the choice menu.

Yipes! Which Foot? The foot is a very old Measure and slightly Different definitions Developed in different Countries. The USGS did all new State Plane coordinate Systems in meters but There are different Definitions of how to Convert meters to feet. In 1927 all conversions were done with U.S. survey feet. In 1983 some people used The international foot and some the U.S. foot. The Illinois Department of Transport. Stayed with the U.S. survey foot. Therefore we will pick the U.S. foot.

We Also Need to Select Our Grid We kind of hope We can all Agree we were In Illinois. Left click on Illinois.

Now We Have to Pick Our Grid (The right side box) Illinois is Divided into Two Transverse Mercator Projection zones (the long Skinning things That run north South) Carbondale Is in the West Zone

So Pick Already! The State Plane Coordinates Were redone in 1983 to fit the North American Datum ellipsoid We will therefore Pick NAD83 and The Illinois West Zone.

I Put in a Set of Latitudes and Longitudes Then I left click the Arrow to convert it Over to Illinois State Plane Coordinates

Out Comes the State Plane Now I could chug through all of my coordinates this way – in fact we will pretend I did and move on to what I will do with this information when I get to MineSight.

Starting a Check Get the Coordinates of Your Points Using the Traverse Calculator Spreadsheet Compare those Coordinates with your GPS coordinates. –Differences of about 10 feet will not be too unusual. –What you are looking for is 100’s of feet of difference that might signal to you a bust in your survey work.

Your Product Turn in a sketch of your traverse loop with the points labeled Turn in a list of the point coordinates from the traverse calculator and then the point coordinates arrived at from GPS You will do this work as individuals.