How to get accurate GPS

In implementing new Customer Information System for Utility companies, data gathering is often required to complete the data that are lacking. Identifying the data that will be gathered is important before going to the field. Additional data can be added since the cost of adding additional data during field campaign less.

GPS coordinate of properties or customers become an important data for the company. The main issue is how to get accurate GPS during field gathering. You can take a look at how the GPS work before designing any activities of GPS gathering in the field.

There are many ways to be considered to get GPS accuracy but from my experiences, the most important is to implement PDOP value in your application. PDOP as defined by GPS Glossary of UIOWA.EDU:

"PDOP: Percent Dilution of Position. Measure of the geometrical strength of the GPS satellite configuration. The amount of error in your position. PDOP less than 4 gives the best accuracy (under 1 meter). Between 4 and 8 gives acceptable accuracy. Greater than 8 gives poor accuracy."

In simple words, the PDOP is an indicator that tell you whether your GPS coordinate that you will take is having enough satellite, enough signal strengths, good satellite positions, etc. The lower the value of PDOP, the better.,

If you want to buy the GPS HHU, ask your vendor if they have PDOP module also installed. If you have bought the GPS HHU, try googling to find PDOP .dll or modules that you can integrate in your HHU applications.

Once you have this module installed, you can always remind your surveyors to get GPS coordinates while the PDOP values shown is as small as possible. This will give you another reminders like:
- avoid too close to tall buildings.
- avoid too close to tress or other obstacles.
- avoid too close to surveyors' body. Yes, your body can block the signal as well.
- and other strategies.

If you want to have better accuracy of GPS, you can even plan the time to do GPS data gathering. All satellites are rotating following their orbits, so you can estimate the best time in your area to have more satellites with more strength. This schedule of satellites are recorded by Almanac. To simplify the discussion, you can try the planning software by Trimble. It is free to try.

I will try to post most of my techniques based on my experiences in GPS gathering in my next post. I hope this can help you. Feel free to leave comments if you have questions or suggestions on how to improve the GPS accuracy during data gathering.