How can you, as a surveyor, use handheld GPS?

An important part of this business column is to give you, the business owner, my ideas on the type of equipment your company may need and the services it may perform in the future. This month I want to focus on GPS technology. If you are the owner of a surveying company and do not have a GPS unit of some type, please read this article carefully-according to Scientific American magazine, September 2003, 20 million people currently use GPS. If your company already utilizes GPS, keep reading for ideas on how to further exploit its money- and time-saving capabilities.

Classes of GPS

I personally separate GPS technology into four different accuracy classes. The first class is what we as surveyors would call survey-grade GPS with sub-millimeter accuracy. Because of the cost of units capable of attaining this level of accuracy (which can range from $20,000 to $75,000), this may not be a feasible level at which to start. The second class is a new series of single-phase centimeter-level GPS receivers that are cost-effective and make a good entry point for users new to the technology. The third class is sub-meter GPS, most commonly referred to as GIS data collection technology. The fourth and final class is the handheld unit, often used by the general public for various, often recreational, activities. These varying levels of GPS are capable of many applications that can save your company time and money.

It would take my next four columns to properly address all the different types of units and applications of millimeter-level GPS technology. If you want to enter this arena or are already using millimeter technology, do your homework carefully when buying or upgrading equipment. The technology is changing and prices continue to drop.

I would, however, like to discuss the centimeter accurate units appearing in the marketplace today. These recent entries into the GPS market do employ some of the older technology and most systems are priced at less than $10,000 with everything you need to be an instant success-even some training. If the people at your company have no GPS experience and are involved in rural surveying projects where tying to section or township corners in the course of your work would be desirable, this would be an excellent level at which to get started with GPS. The centimeter accuracy is well within the accuracy required for rural surveys in most states. Keep in mind, though, that this technology does require the unit to gather data at each point for a considerable length of time. Field demonstrations can be arranged with companies that sell GPS equipment.

The handheld GPS unit can be purchased for as little as $200 at most local discount electronics stores. Spending slightly more will get you additional features such as Wide Area Augmentation System (WAAS) support, or an onboard map of roads and features. These types of units cost less than $500 and may be one of the best investments you ever make.

One important thing to know about handhelds is that most read in latitude and longitude. Also, they do not read in seconds of a degree, but rather in degrees and minutes to three decimal places. To get seconds you need to convert decimal minutes to minutes and seconds. On a recent fishing trip to Canada with my brother, we left three different makes and models of handheld GPS units outside for about an hour to check one against the other. At the end of the hour, two of the units read degrees and seconds to the same three decimal places. The other unit read the same latitude and was off by one decimal place in longitude (about 5 feet). Needless to say, I was pleasantly surprised.

Maximizing Your Handheld

When you purchase your unit and install the batteries, take it outside and turn it on. Let it sit somewhere with a clear view of the sky for about 30 minutes to allow the unit to initialize all its settings. Take this time to read the manual. When the unit is finished initializing, pick it up and begin exploring its functions. The first screen on most units shows a diagram of the sky depicting the location of satellites and along the bottom is a graph showing the strength of each satellite. Walk around with the unit and see how obstacles such as trees and buildings affect the signal-even better, take it for a ride in your vehicle. The latitude and longitude will change about one minute per mile. If you purchased a unit with mapping ability, turn on the map feature and watch it navigate your position on the screen. All units run on batteries but can also be hooked up to your vehicle's electrical system.

Now that you know how your unit works, how can you use this knowledge to make money? All handheld units can be connected to a computer. Using software such as Delorme Street Atlas allows you to locate a parcel of land by address or street location. The location will provide you with latitude and longitude of the parcel; this in turn will let you navigate directly to the parcel using the GPS unit. Saving the survey crew time in finding a survey site can result in cost savings for the company.

Another great use is to help find the parcel corners on a survey project. This can be done by looking up a parcel to be surveyed on the digital topo quads for your state, identifying the property corners, and recording their latitude and longitude. Programming these locations into your handheld GPS unit as waypoints will allow you to walk to each corner within 10 or 15 feet, saving time and saving money. I think that in the future survey plats will require state plane coordinates or latitude and longitude. Why not get the jump on this and include the latitude and longitude under your location map? This also makes it easier for the next surveyor to find the location.

What about field checking? It seems to me that in surveying we have all but given up on field checking of survey work. I know many companies do cell tower locations and use only GPS technology. A lot of liability rides on the technology used to perform this type of survey. Verifying positions with a handheld GPS unit while the original survey is in progress, or as a final check on other GPS equipment, could save your company from trouble. Also, what about checking the final plat? When the final map is finished and before it is sent to the client, look up the final coordinates in your digital topo quads for the state where the survey is located. Check to make sure the survey fits that location, including the elevation. Be aware that the elevation is only going to check within about 20 feet.

If you have not yet entered the world of GPS technology, give yourself and your crews a great Christmas present. Equip them with at least a handheld unit. Take my word on this; you can't afford not to get involved in GPS.