On 16-12-2011 03:31, Stephen Mather wrote:
Hmm. I don't follow? The revision would be this:float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData) { // Hydrologic Slope is the max // local slope btw center cell and adjacent cells const double radiansToDegrees = 180.0 / M_PI; GDALSlopeAlgData* psData = (GDALSlopeAlgData*)pData; double key; float pafLocalMin = afWin[0]; float pafLocalMax = afWin[0]; for ( int k = 1; k < 9; k++) { if (afWin[k] < pafLocalMin) { pafLocalMin=afWin[k]; } if (afWin[k] > pafLocalMax) { pafLocalMax=afWin[k]; } } key = afWin[4] - pafLocalMin; if (psData->slopeFormat == 1)return (float) (atan(sqrt(key) / (2*psData->scale)) * radiansToDegrees);else return (float) (100*(sqrt(key) / (2*psData->scale))); } But, clearly I'm not understanding something about the window.
Steve, there are more things I do not understand either. What is 'psData->scale'? Is it the grid cell size? So, if 'pafLocalMin' is on one of the 4 corners the distance is not cell size (let's call it DX) but instead sqrt(DX*DX + DX*DX). And what if data is in geogs? Than DX is clearly different from DY and changes with latitude. You need to take that into account to compute the slope.
Joaquim _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
