Photosensitive means for controlling leveling and grading apparatus and establishing reference levels

Claim 1

IN EQUIPMENT FOR USE IN LEVELING AND GRADING AND THE LIKE: A MOBILE DEVICE WHOSE ELEVATION IS TO BE DETERMINED WITH RESPECT TO A REFERENCE STATION, SAID DEVICE INCLUDING APPARATUS FOR RADIATING ELECTROMAGNET WAVES AND MEANS FOR ALTERING THE ELEVATION OF SAID APPARATUS; AND A REFERENCE STATION COMPRISING A FIRST REFLECTING MEMBER FOR DIRECTING IN A GENERALLY UPWARD DIRECTION SUCH ELECTROMAGNETIC WAVES AS MAY FALL THEREUPON, A SECOND REFLECTING MEMBER ADJACENT TO THE SAID FIRST MEMBER FOR DIRECTING IN A GENERALLY DOWNWARD DIRECTION SUCH ELECTROMAGNETIC WAVES AS MAY REACH SAID SECOND MEMBER, A FIRST RADIATION SENSITIVE INSTRUMENT DISPOSED IN THE PATH OF WAVES REFLECTED FROM SAID FIRST MEMBER, A SECOND RADIATION SENSITIVE INSTRUMENT DISPOSED IN THE PATH OF WAVES REFLECTED FROM SAID SECOND MEMBER, A RADIATION SHIELD SURROUNDING SAID MEMBERS, SAID SHIELD HAVING A CHANNEL THERETHROUGH TO PERMIT RADIATION TO PASS FROM SAID APPARATUS TOWARD SAID MEMBERS, MEANS FOR LEVELING AT LEAST THE PORTION OF SAID STATION THAT EMBODIES SAID CHANNEL, AND MEANS FOR TRANSMITTING INFORMATION REGARDING THE RELATIVE AMOUNT OF RADIATION REACHING SAID FIRST AND SECOND INSTRUMENTS.