[MetaCRS] csmap - distance calculation

[Andre Barth]

Hi Norman,

What you're looking for should be possible – even though I'm not quite clear about what you mean by "… Add metres to it…"

What's the source & target EPSG ID, btw? CS-Map doesn't support all EPSG coordinate reference systems, but a good amount of it.

But let me test my understanding here:

For a given EPSG 'coordinate reference system' (assuming CS-Map has support for it), you need to convert/transform a point to a different 'coordinate reference system', which, in your case, happens to be a projected system which uses a spherical projection (which?) ?

This you can do using the CS_cnvrt function (in forward and inverse direction).


double xyz [3];


xyz [0] = 0.0;

xyz [1] = 20000000.000;

xyz [2] = 0.0;


int st = CS_cnvrt ("WGS84.PseudoMercator","LL",xyz);

Note though, that this requires you to supply CS-Map (string) IDs – not EPSG Ids


CSepsg2adskCS() does the mapping.


BTW – are you just interested in calculating a point which does have an offset to the given original point?

If so, you might want to look into

CS_azddll

which calculates a LL (long lat) target point from a source LL coordinate pair, azimuth & distance (i.e. meter). The LL point for your projected coordinates (and vice versa) you can retrieve using the CS_cs2ll and CS_ll2cs functions, respectively.

HTH,
Andre


On 3/20/13 10:36 PM, "Norman Barker" <norman.barker at gmail.com<mailto:norman.barker at gmail.com>> wrote:

Hi,

I am using csmap for the first time and I have been able to get it
compiled on mac. I am interested in how I take a point in a particular
projection (for now defined by an epsg code) and convert this to a
spherical projection and add metres to it and then reverse this
transform. I am trying to do the same as the PostGIS Geographic type
but using CsMap to do a radius search, I will then use geos to buffer
the original centre point by the distance (in the original
coordinates).

Is this possible?

thanks,

Norman
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