+/* return the nearest waypoint */
+int8_t xycoord_to_ijcoord(int16_t *xp, int16_t *yp, uint8_t *ip, uint8_t *jp);
+
+/* return the nearest waypoint that is not a corn: xp and yp contains
+ * the input and output, and ip, jp are only outputs. return 0 on
+ * success. */
+int8_t xycoord_to_ijcoord_not_corn(int16_t *xp, int16_t *yp, uint8_t *ip, uint8_t *jp);
+