How can we perform Differential GPS technique in simple way?

Differential GPS is useful to reduce errors when taking coordinates readings of a point on earth. in fact, and due to many reasons when we take latitude and logitude of a point using our standard GPS receiver , the readings will be shown somewhere els !

There is so many ways to reduce errors

one is and less coastly , using two receivers and set one as a base station ... the question is HOW ??

Appreciate everyone who tried and simplified it here for me

Thanks in advance

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You have received two excellent answers so far. But I think you are still wondering how to do a differential land survey, right? Can you get hold of two GPS and two laptop PCs? It is then just a matter of registering the two positions and time sets and compare them later. I don't know your budget for this project but you could e.g. buy cheap PDA with GPS incorportated. You'll find cheap ones like Mio and Acer. You'll most probably find also freeware or shareware that reads the NMEA port of the GPS and creates a file with position and time. Then you might want to write your own application that reads both files, compare position for the same time and calculate the offset in whatever unit you want. Most probably when working at this accuracy, your geographical position is not important, only the relative one from one GPS to the other. But if you have a map reference, you can trace it from that. As a warning, don't use GWS84 references on an old map. I know from experience that e.g. nautical charts may be very relatively accurate but inaccurate to a common world reference such as GWS84.

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I generally use UTM grid coordinates simply because they're smaller and easier to make sense of.

But I'm mystified by your conjecture that large errors occur on a properly functioning GPS with any meaningful frequency.

I've used GPS instruments almost from the time they first came available to the public when they had a 'built-in' error factor, and only one one occasion have I experienced an error such as you describe.
Differential GPS works based on the fact that there are spatially correlated errors in GPS computations (based on variable signal delays due to atmospheric conditions, among other things). By spatially correlated, I mean that the error value is based on one's position on the ground. The error value on a global scale may be somewhat random, but within any local area (1 or 2 miles) the error value is relatively constant.

A ground based GPS reference station, at a known, precisely surveyed position, can compare the GPS calculated position against its known position and compute the local error value. It can then broadcast that local error value to all GPS receivers in the local vicinity. Since the range of that broadcast will be small (1 to 2 miles) all GPS receivers that receive that correction factor will have about the same positional error and so can correct their own measurements accordingly. If you put one of these base stations on ever cell phone tower, then the hand held GPS can select the reference with the strongest signal strength (presumably the closest unit).
First, DGPS is usually no longer required. President Clinton ordered the civilian GPS to have most of the error taken out. It is now accurate to 10 meters.

If the error is reinstated, or you need ultra accurate GPS, you should know that the two GPS receivers dance the same dance around the actual point. SOoooo.... Put one GPS receiver on a KNOWN point. Sample the GPS position every second. Calculate its error from the true known point and record it every second. Add a time stamp to the Lat and Long. This time stamp will let the rover know which set of coordinates to modify with what factors.

Transmit this error info to the roving GPS receiver and subtract it from the GPS position of the rover. The rover will now have its true position.

This system requires a fairly expensive transmitter receiver. For most applications. regular GPS receivers are just fine. What application are you trying to do?