PDA

View Full Version : Gps



Jerry Thompson
07-23-2016, 12:58 PM
How were street and road maps transformed into the data base in use today?

Matt Day
07-23-2016, 1:54 PM
Computers, satellites, people to push a few buttons...

http://www.extremetech.com/extreme/210893-extremetech-explains-how-does-gps-work

Gail Ludwig
07-23-2016, 3:21 PM
They usually use either satellite imagery or high altitude images or some type of air photos. These are stitched together and adjusted for the curvature of the earth (geo-referenced). Then they run a pattern recognition program that identifies roads and other features. These are usually in cell format (raster) which then are run through another program which changes the cells to lines (vector). Finally a person will go through and edit the lines and piece them together. They also will label each of the lines (geo-code). It is a long and tedious process --but technology is making it much faster and more accurate. The job market for people who do this type of work is BOOMING. Major in Geography and specialize in Geographic Information Systems and you will have a job for life!!

Jerry Thompson
07-23-2016, 4:21 PM
Thank you fellas. It is all above my pay grade but very interesting.

Ole Anderson
07-25-2016, 1:18 PM
They usually use either satellite imagery or high altitude images or some type of air photos. These are stitched together and adjusted for the curvature of the earth (geo-referenced). Then they run a pattern recognition program that identifies roads and other features. These are usually in cell format (raster) which then are run through another program which changes the cells to lines (vector). Finally a person will go through and edit the lines and piece them together. They also will label each of the lines (geo-code). It is a long and tedious process --but technology is making it much faster and more accurate. The job market for people who do this type of work is BOOMING. Major in Geography and specialize in Geographic Information Systems and you will have a job for life!!

Sounds like one of the most boring jobs in the world. I was in HS (1960's) and offered a summer job drawing elevation contours using a pair of stereo aerial photographs. No thanks. Now it is all done by computer with just some hand touch-ups. In the late 1930's my dad was a survey crew chief for the Michigan Highway Department and the survey crew numbered at least 7 persons. Today my buddy is a one man survey crew running state of the art GPS accurate to 1/4" anyplace you can see the sky.

Alan Rutherford
07-26-2016, 10:57 AM
I was in the satellite business years ago (tracking) and computers and especially databases after that. The GPS satellite technology is impressive but IMO the database component is truly mind-blowing. My first GPS held crude map data for a fraction of a state. To go somewhere else I had to connect to a PC, delete that data and load some more. Today if I'm driving down a country road anywhere in the country and pass a sign with a speed limit change, the GPS usually displays the change within about 50 feet of the sign. Incredible stuff!!