Add calculation of difference between auto-correct bed level plane, a…

…nd measured topo map.

Marlin/Marlin_main.cpp

@@ -2488,6 +2488,9 @@ inline void gcode_G28() {
           }
         }
 
+        if (!dryrun) set_bed_level_equation_lsq(plane_equation_coefficients);
+        free(plane_equation_coefficients);
+
         // Show the Topography map if enabled
         if (do_topography_map) {
 
@@ -2498,10 +2501,22 @@ inline void gcode_G28() {
           SERIAL_PROTOCOLPGM("|...Front...|\n");
           SERIAL_PROTOCOLPGM("+-----------+\n");
 
+	  float min_diff = 999;
+
           for (int yy = auto_bed_leveling_grid_points - 1; yy >= 0; yy--) {
             for (int xx = 0; xx < auto_bed_leveling_grid_points; xx++) {
               int ind = yy * auto_bed_leveling_grid_points + xx;
               float diff = eqnBVector[ind] - mean;
+
+	      float x_tmp = eqnAMatrix[ind + 0 * abl2],
+                y_tmp = eqnAMatrix[ind + 1 * abl2],
+                z_tmp = 0;
+
+	      apply_rotation_xyz(plan_bed_level_matrix,x_tmp,y_tmp,z_tmp);
+
+	      if (eqnBVector[ind] - z_tmp < min_diff)
+                min_diff = eqnBVector[ind] - z_tmp;
+
               if (diff >= 0.0)
                 SERIAL_PROTOCOLPGM(" +");   // Include + for column alignment
               else
@@ -2512,11 +2527,30 @@ inline void gcode_G28() {
           } // yy
           SERIAL_EOL;
 
-        } //do_topography_map
+	  SERIAL_PROTOCOLPGM(" \nCorrected Bed Height vs. Bed Topology: \n");
 
+          for (int yy = auto_bed_leveling_grid_points - 1; yy >= 0; yy--) {
+            for (int xx = 0; xx < auto_bed_leveling_grid_points; xx++) {
+              int ind = yy * auto_bed_leveling_grid_points + xx;
+              float x_tmp = eqnAMatrix[ind + 0 * abl2],
+                y_tmp = eqnAMatrix[ind + 1 * abl2],
+                z_tmp = 0;
 
-        if (!dryrun) set_bed_level_equation_lsq(plane_equation_coefficients);
-        free(plane_equation_coefficients);
+              apply_rotation_xyz(plan_bed_level_matrix,x_tmp,y_tmp,z_tmp);
+
+              float diff = eqnBVector[ind] - z_tmp - min_diff;
+              if (diff >= 0.0)
+                SERIAL_PROTOCOLPGM(" +");
+              // Include + for column alignment
+              else
+                SERIAL_PROTOCOLCHAR(' ');
+              SERIAL_PROTOCOL_F(diff, 5);
+            } // xx
+            SERIAL_EOL;
+          } // yy
+          SERIAL_EOL;
+
+        } //do_topography_map
 
       #endif //!DELTA