In order to measure momentary speed, first I need to measure the distance between two pairs of coordinates. That's where my lack of knowledge stops me.
I have example data in NMEA format:
$GPGGA,002246,3918.5986,N,11954.1140,W,1,08,2.3,2697.9,M,-22.4,M,,*4C
(...)
$GPGGA,002248,3918.5887,N,11954.1395,W,1,08,2.4,2696.5,M,-22.4,M,,*42
I figured out that data above gives me following information, needed to measure the distance:
-
- Coordinates:
39 deg 18.5986' N
,119 deg 54.1140' W
- Altitude (above sea level):
2697.9 m
- Height of geoid above WGS84 elipsoid:
-22.4 m
- Coordinates:
-
- Coordinates:
39 deg 18.5887' N, 119 deg 54.1395' W
- Altitude (above sea level):
2696.5 m
- Height of geoid above WGS84 elipsoid:
-22.4 m
- Coordinates:
Angular distance between this two points is: latitude -0,0099'
, longitude 0.0255'
.
The difference between altitudes is -1,4 m
.
And there I'm stuck. And my question is – how to measure the distance between those two points in (kilo)meters?
I think it's worth repeating that the distance would be very small, because it's needed to calculate a momentary speed. So I think the data emphasized above (the height of a geoide) could improve precision.
Best Answer
If your data is in a cartesian/rectangular coordinate system you could simply do 2 pythagorean calculations... where the first one would calculate the distance in XY plane, where a would be x1-x2 and b would be y1-y2. The second calculation would use the result from the first calculation as a and b would be z1-z2.
perhaps something like this