Minor tweaks from last round of photo inserting.

src/Prep/Photo/Makefile.am

@@ -25,7 +25,7 @@
 
 EXTRA_DIST = chop.pl trans.pl
 
-bin_PROGRAMS = photo wgs84offset
+bin_PROGRAMS = photo wgs84offset findcorners
 
 photo_SOURCES = photo.cxx
 
@@ -43,6 +43,10 @@ wgs84offset_SOURCES = wgs84offset.cxx
 
 wgs84offset_LDADD = -lsgmath -lsgdebug
 
+findcorners_SOURCES = findcorners.cxx
+
+findcorners_LDADD = -lsgmath -lsgdebug
+
 INCLUDES += \
 	-I$(top_srcdir) \
 	-I$(top_srcdir)/src \

src/Prep/Photo/chop.pl

@@ -21,7 +21,7 @@ $basename = $file;
 $basename =~ s/\.png$//;
 
 # convert source image to pnm
-# `pngtopnm $basename.png > $basename.pnm`
+`pngtopnm $basename.png > $basename.pnm`;
 
 $dx = $width / $xdiv;
 $dy = $height / $ydiv;

src/Prep/Photo/findcorners.cxx

@@ -0,0 +1,105 @@
+// find (lat/lon) of each corner of an image
+
+#include <stdlib.h>
+
+#include <simgear/math/sg_geodesy.hxx>
+
+int main( int argc, char **argv ) {
+
+    if ( argc != 11 ) {
+        cout << "Usage: " << argv[0]
+             << "xres yres xrwy1(px) yrwy1(px) xrwy2(px) yrwy2(px) rwy_len(ft) rwy_angle(deg) rwy_cent_lon(deg) rwy_cent_lat(deg)" << endl;
+        cout << "if you are at rwy1 looking at rwy2 you will be facing rwy_angle" << endl;
+	exit(-1);
+    }
+
+    int xres = atoi( argv[1] );
+    int yres = atoi( argv[2] );
+    int xrwy1 = atoi( argv[3] );
+    int yrwy1 = atoi( argv[4] );
+    int xrwy2 = atoi( argv[5] );
+    int yrwy2 = atoi( argv[6] );
+    double len = atof( argv[7] );
+    double true_angle = atof( argv[8] ) * SGD_DEGREES_TO_RADIANS;
+    double clon = atof( argv[9] );
+    double clat = atof( argv[10] );
+
+    // find runway center in pixel space
+    double xcen = (double)(xrwy1 + xrwy2) / 2.0f;
+    double ycen = (double)(yrwy1 + yrwy2) / 2.0f;
+    cout << "runway center (pixels) = " << xcen << ", " << ycen << endl;
+
+    // find runway distance in pixels
+    int dx = xrwy2 - xrwy1;
+    int dy = yrwy2 - yrwy1;
+    cout << "dx = " << dx << " dy = " << dy << endl;
+    double distp = sqrt( dx*dx + dy*dy );
+    cout << "runway distance (pixels) = " << distp << endl;
+
+    // find pixel resolution
+    double pixel_to_feet = len / distp;
+    double feet_to_pixel = distp / len;
+    cout << "feet per pixel = " << pixel_to_feet << endl;
+    cout << "pixel per feet = " << feet_to_pixel << endl;
+
+    // find runway angle in image space
+    double img_angle = atan2( dy, dx );
+    cout << "runway angle in image space = "
+         << img_angle * SGD_RADIANS_TO_DEGREES << endl;
+    // angle offset
+    double angle_offset = true_angle - img_angle;
+    cout << "angle offset = " << angle_offset * SGD_RADIANS_TO_DEGREES << endl;
+
+    cout << "true runway hdg = "
+         << (img_angle + angle_offset) * SGD_RADIANS_TO_DEGREES << endl;
+
+    // setup image corner coordinates
+    int corner[4][2];
+    corner[0][0] = 0;    corner[0][1] = 0;
+    corner[1][0] = xres; corner[1][1] = 0;
+    corner[2][0] = xres; corner[2][1] = yres;
+    corner[3][0] = 0;    corner[3][1] = yres;
+
+    // calculate corresponding corner angles from runway center
+    double angles_image[4];     // angles in image space
+    double angles_true[4];      // true / real world angles of corners
+    double dist_px[4];          // distance in pixels from rwy center to corner
+    double dist_m[4];           // distance in meters
+    for ( int i = 0; i < 4; ++i ) {
+        double xdist = corner[i][0] - xcen;
+        double ydist = corner[i][1] - ycen;
+        angles_image[i] = atan2( ydist, xdist );
+        angles_true[i] = angles_image[i] + angle_offset;
+        dist_px[i] = sqrt( xdist*xdist + ydist*ydist );
+        dist_m[i] = dist_px[i] * pixel_to_feet * 0.3048;
+        cout << "corner " << i << " (" << corner[i][0] << "," << corner[i][1]
+             << ")" << endl;
+        cout << "  angle to (image space ) = "
+             << angles_image[i] * SGD_RADIANS_TO_DEGREES << endl;
+        cout << "  angle to (real world ) = "
+             << angles_true[i] * SGD_RADIANS_TO_DEGREES << endl;
+        cout << "  distance to = " << dist_px[i] << " (px)  "
+             << dist_m[i] << " (m)" << endl;
+
+        /**
+         * Given a starting position and an offset radial and distance,
+         * calculate an ending positon on a wgs84 ellipsoid.
+         * @param alt (in) meters
+         * @param lat1 (in) degrees
+         * @param lon1 (in) degrees
+         * @param az1 (in) degrees
+         * @param s (in) distance in meters
+         * @param lat2 (out) degrees
+         * @param lon2 (out) degrees
+         * @param az2 (out) return course in degrees
+         */
+
+        double lat2, lon2, az2;
+        double alt = 0;
+        geo_direct_wgs_84 ( alt, clat, clon,
+                            angles_true[i] * SGD_RADIANS_TO_DEGREES, dist_m[i],
+                            &lat2, &lon2, &az2 );
+        printf("  pos = %.6f %6f\n", lon2, lat2 );
+    }
+    
+}

src/Prep/Photo/wgs84offset.cxx

@@ -10,7 +10,9 @@ SG_USING_STD(endl);
 int main( int argc, char **argv ) {
 
     if ( argc != 6 ) {
-        cout << "bad usage ..." << endl;
+        cout << "Usage: " << argv[0]
+             << " lon1 lat1 alt azimuth(deg) distance(m)" << endl;
+	exit(-1);
     }
 
     double lon1 = atof( argv[1] );