Allow additional or non-standard terrain source directories to be specified

on the command line with the --terrain= option.  You can specify as many as you like.  Directories specified on the command line will take precidence over
the default directories and the directories will be searched in the order
specified.

src/Airports/GenAirports/apt_surface.cxx

@@ -37,13 +37,14 @@ SG_USING_NAMESPACE( PLib );
 
 
 // fix node elevations.  Offset is added to the final elevation
-static void calc_elevations( const string &root, Matrix_Point3Df &Pts ) {
+static void calc_elevations( const string &root, const string_list elev_src,
-    string_list elev_src;
+                             Matrix_Point3Df &Pts ) {
-    elev_src.clear();
+    // string_list elev_src;
-    elev_src.push_back( "SRTM-1" );
+    // elev_src.clear();
-    elev_src.push_back( "SRTM-3" );
+    // elev_src.push_back( "SRTM-1" );
-    elev_src.push_back( "DEM-3" );
+    // elev_src.push_back( "SRTM-3" );
-    elev_src.push_back( "DEM-30" );
+    // elev_src.push_back( "DEM-3" );
+    // elev_src.push_back( "DEM-30" );
 
     bool done = false;
     int i, j;
@@ -164,6 +165,7 @@ static void calc_elevations( const string &root, Matrix_Point3Df &Pts ) {
 // Constructor, specify min and max coordinates of desired area in
 // lon/lat degrees
 TGAptSurface::TGAptSurface( const string& path,
+                            const string_list& elev_src,
                             Point3D _min_deg, Point3D _max_deg )
 {
     // Calculate desired size of grid
@@ -208,7 +210,7 @@ TGAptSurface::TGAptSurface( const string& path,
     }
 
     // Determine elevation of the grid points
-    calc_elevations( path, dPts );
+    calc_elevations( path, elev_src, dPts );
 
     // Build the normal res input grid from the double res version
     Matrix_Point3Df Pts(xdivs + 1, ydivs + 1);

src/Airports/GenAirports/apt_surface.hxx

@@ -61,7 +61,8 @@ public:
 
     // Constructor, specify min and max coordinates of desired area in
     // lon/lat degrees
-    TGAptSurface( const string &path, Point3D _min_deg, Point3D _max_deg );
+    TGAptSurface( const string &path, const string_list& elev_src,
+                  Point3D _min_deg, Point3D _max_deg );
 
     // Destructor
     ~TGAptSurface();

src/Airports/GenAirports/build.cxx

@@ -323,7 +323,9 @@ static void build_runway( const TGRunway& rwy_info,
 // build 3d airport
 void build_airport( string airport_id, float alt_m,
                     string_list& runways_raw,
-                    string_list& taxiways_raw, const string& root )
+                    string_list& taxiways_raw,
+                    const string& root,
+                    const string_list& elev_src )
 {
     int i, j, k;
 
@@ -911,7 +913,7 @@ void build_airport( string airport_id, float alt_m,
     min_deg.setlat( min_deg.lat() - 0.1 * dlat );
     max_deg.setlat( max_deg.lat() + 0.1 * dlat );
 
-    TGAptSurface apt_surf( root, min_deg, max_deg );
+    TGAptSurface apt_surf( root, elev_src, min_deg, max_deg );
     cout << "Surface created" << endl;
 
     // calculate node elevations

src/Airports/GenAirports/build.hxx

@@ -35,7 +35,9 @@
 
 // build 3d airport
 void build_airport( string airport_id, float alt_m, string_list& runways_raw,
-                    string_list& taxiways_raw, const string& root );
+                    string_list& taxiways_raw,
+                    const string& root,
+                    const string_list& elev_src );
 
 
 

src/Airports/GenAirports/main.cxx

@@ -76,6 +76,9 @@ int main( int argc, char **argv ) {
     float max_lat = 90;
     bool ready_to_go = true;
 
+    string_list elev_src;
+    elev_src.clear();
+
     sglog().setLogLevels( SG_GENERAL, SG_INFO );
 
     // parse arguments
@@ -89,6 +92,8 @@ int main( int argc, char **argv ) {
             work_dir = arg.substr(7);
 	} else if ( arg.find("--input=") == 0 ) {
 	    input_file = arg.substr(8);
+        } else if ( arg.find("--terrain=") == 0 ) {
+            elev_src.push_back( arg.substr(10) );
  	} else if ( arg.find("--start-id=") == 0 ) {
 	    start_id = arg.substr(11);
 	    ready_to_go = false;
@@ -114,7 +119,16 @@ int main( int argc, char **argv ) {
 	}
     }
 
+    elev_src.push_back( "SRTM-1" );
+    elev_src.push_back( "SRTM-3" );
+    elev_src.push_back( "DEM-3" );
+    elev_src.push_back( "DEM-30" );
+
     SG_LOG(SG_GENERAL, SG_INFO, "Input file = " << input_file);
+    SG_LOG(SG_GENERAL, SG_INFO, "Terrain sources = ");
+    for ( unsigned int i = 0; i < elev_src.size(); ++i ) {
+        SG_LOG(SG_GENERAL, SG_INFO, "  " << work_dir << "/" << elev_src[i] );
+    }
     SG_LOG(SG_GENERAL, SG_INFO, "Work directory = " << work_dir);
     SG_LOG(SG_GENERAL, SG_INFO, "Nudge = " << nudge);
     SG_LOG(SG_GENERAL, SG_INFO, "Longitude = " << min_lon << ':' << max_lon);
@@ -215,7 +229,7 @@ int main( int argc, char **argv ) {
                         try {
                             build_airport( last_apt_id, elev * SG_FEET_TO_METER,
                                            runways_list, taxiways_list,
-                                           work_dir );
+                                           work_dir, elev_src );
                         } catch (sg_exception &e) {
                             SG_LOG( SG_GENERAL, SG_ALERT,
                                     "Failed to build airport = "
@@ -286,7 +300,7 @@ int main( int argc, char **argv ) {
                     try {
                         build_airport( last_apt_id, elev * SG_FEET_TO_METER,
                                        runways_list, taxiways_list,
-                                       work_dir );
+                                       work_dir, elev_src );
                     } catch (sg_exception &e) {
                         SG_LOG( SG_GENERAL, SG_ALERT,
                                 "Failed to build airport = "