Now, our globe is divided into horizontal and vertical grids wherein the grid lines run parallel to each other.
The vertical ones that is the longitudes intersect at the poles while the horizontal ones
the latitudes, are always parallel to each other.
The latitudes are marked zero at the equator and go upto 90 degrees at the poles.
For example, currently i am in the city of Bangalore and my current location is 12.979831, 77.606328
If i put on google maps i can see it.
This is exactly where I am. Notice that this has six decimals of accuracy.
Lets understand this Now, One degree of latitude covers about 111.11 km. (A longitude also covers almost similar distance)
Hence, the first decimal place gives us the accuracy of up to 11.1 km: it can distinguish
the position of one large city from a neighboring large city.
The second decimal place gives us the accuracy of up to 1.1 km:
it can separate one village from the next.
Similarly the third decimal place is up to 110 m and the the fourth ,up to 11m:
The fifth decimal place gives us the accuracy of up to 1.1 m: Accuracy of this level can be used
to say, distinguish position of one tree from another. Accuracy to this level or more with commercial
GPS units can only be achieved with differential correction.
I will cover differential correction in the next lecture... The sixth decimal place gives us the accuracy of up to 0.11 m
you can use this for laying out structures in detail, for designing landscapes and building roads.
The seventh decimal place gives us an accuracy of up to 11 mm
This is needed in very few specialized cases and is near the limit of what GPS-based techniques can achieve.