//------------------------------------------------------------------------------
// Locates an elevation value (meters) for a given reference point and returns
// it in 'elev'. Function returns true if successful, otherwise 'elev' is unchanged.
//------------------------------------------------------------------------------
bool QuadMap::getElevation(
LCreal* const elev, // The elevation value (meters)
const double lat, // Reference latitude (degs)
const double lon, // Reference longitude (degs)
const bool interp // Interpolate between elevation posts (if true)
) const
{
// Early out tests
if ( !isDataLoaded() || // Not loaded or
(lat < getLatitudeSW() ||
lat > getLatitudeNE()) || // wrong latitude or
(lon < getLongitudeSW() ||
lon > getLongitudeNE()) // wrong longitude
) return false;
LCreal value = 0.0; // the elevation (meters)
bool found = false;
for (unsigned int i = 0; i < numDataFiles && !found; i++) {
found = dataFiles[i]->getElevation(&value, lat, lon, interp);
}
if (found) {
*elev = value;
}
return found;
}
//------------------------------------------------------------------------------
// Computes the nearest row index for the latitude (degs).
// Returns true if the index is valid
//------------------------------------------------------------------------------
bool DataFile::computerRowIndex(unsigned int* const irow, const double lat) const
{
// Early out tests
if ( (lat < getLatitudeSW() ||
lat > getLatitudeNE()) || // the latitude's out of range, or
(irow == 0) || // the 'irow' pointer wasn't provided, or
!isDataLoaded() // the data isn't loaded
) return false;
// Locate row (latitude) index
double points = (lat - getLatitudeSW()) / latSpacing;
if (points < 0) points = 0;
unsigned int idx = static_cast<unsigned int>(points + 0.5);
if (idx >= nptlat) idx = (nptlat-1);
*irow = idx;
return true;
}
//------------------------------------------------------------------------------
// Locates an elevation value (meters) for a given reference point and returns
// it in 'elev'. Function returns true if successful, otherwise 'elev' is unchanged.
//------------------------------------------------------------------------------
bool DataFile::getElevation(
LCreal* const elev, // The elevation value (meters)
const double lat, // Reference latitude (degs)
const double lon, // Reference longitude (degs)
const bool interp // Interpolate between elevation posts (if true)
) const
{
LCreal value = 0; // the elevation (meters)
// Early out tests
if ( !isDataLoaded() || // Not loaded or
(lat < getLatitudeSW() ||
lat > getLatitudeNE()) || // wrong latitude or
(lon < getLongitudeSW() ||
lon > getLongitudeNE()) // wrong longitude
) return false;
// ---
// Compute the lat and lon points
// ---
double pointsLat = (lat - getLatitudeSW()) / latSpacing;
if (pointsLat < 0) pointsLat = 0;
double pointsLon = (lon - getLongitudeSW()) / lonSpacing;
if (pointsLon < 0) pointsLon = 0;
// ---
// Interpolating between elevation posts?
// ---
if (interp) {
// Yes ---
// South-west corner post is [icol][irow]
unsigned int irow = static_cast<unsigned int>(pointsLat);
unsigned int icol = static_cast<unsigned int>(pointsLon);
if (irow > (nptlat-2)) irow = (nptlat-2);
if (icol > (nptlong-2)) icol = (nptlong-2);
// delta from s-w corner post
LCreal deltaLat = static_cast<LCreal>(pointsLat - static_cast<double>(irow));
LCreal deltaLon = static_cast<LCreal>(pointsLon - static_cast<double>(icol));
// Get the elevations at each corner
LCreal elevSW = static_cast<LCreal>(columns[icol][irow]);
LCreal elevNW = static_cast<LCreal>(columns[icol][irow+1]);
LCreal elevSE = static_cast<LCreal>(columns[icol+1][irow]);
LCreal elevNE = static_cast<LCreal>(columns[icol+1][irow+1]);
// Interpolate the west point
LCreal westPoint = elevSW + (elevNW - elevSW) * deltaLat;
// Interpolate the east point
LCreal eastPoint = elevSE + (elevNE - elevSE) * deltaLat;
// Interpolate between the west and east points
value = westPoint + (eastPoint - westPoint) * deltaLon;
}
else {
// No -- just use the nearest post
// Nearest post
unsigned int irow = static_cast<unsigned int>(pointsLat + 0.5f);
unsigned int icol = static_cast<unsigned int>(pointsLon + 0.5f);
if (irow >= nptlat) irow = (nptlat-1);
if (icol >= nptlong) icol = (nptlong-1);
// Get the elevation post at the current indices.
value = static_cast<LCreal>(columns[icol][irow]);
}
// ---
// Return the elevation value to the user
// ---
*elev = value;
return true;
}
