GPS

  • mike_j
    Nashua Iowa
    Posts: 754
    #1245429

    I recently bought a handheld GPS in the hopes that it would help me find some of the rock piles, bridges and brush piles the Iowa DNR has given us the coordinents to on recently built lakes. Tryed it out and still couldn’t find any of this marked structure. Mentioned this to a guy at a bait shop and was told that the government changed the coordinents of the GPS system after 911 so anything marked before that would no longer have the correct coordinents. Has any one else heard this.

    amwatson
    Holmen,WI
    Posts: 5130
    #336994

    Sounds a little fishy to me. Correct me if I am wrong, but you can’t just “change” the latitude and longitude of the world. The problem could be that you were close to the structure but didn’t find them. It seems to me that my GPS is not exactly on, it will get you within so many feet, but not dead on a given coordinate. Once you are close, you will have to do a little searching.

    mike_j
    Nashua Iowa
    Posts: 754
    #336995

    I thought that sounded a little strange too. thanks for the info.

    dm5000
    Des Moines, IA
    Posts: 199
    #336996

    Your bait shop friend is behind the times. There was something called “selective availability” which for a brief time reduced the accuracy of civilian GPS, but that has been undone and if your WAAS indicator is on, you whould be within about a yard of the correct coordinates. Perhaps you are not getting your WAAS signal.

    Dave

    theduck
    Posts: 149
    #336997

    They can’t change the coordinates but I found on an iowa lake that the structure I was looking for has not been covered with water yet. This was on Belva deer lake. I was looking for a hump and It had me really close to shore and if I would have walked to the hump I would have been on shore. I thought my gps was acting up but after I looked around I could see that the hump on shore was man made.The lake was just not full to that point yet.

    dm5000
    Des Moines, IA
    Posts: 199
    #336998

    Here is the President’s speech when selective availability was “undone” almost 5 years ago:

    THE WHITE HOUSE
    Office of the Press Secretary
    For Immediate Release May 1, 2000
    STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES’ DECISION TO STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY

    Today, I am pleased to announce that the United States will stop the intentional degradation of the Global Positioning System (GPS) signals available to the public beginning at midnight tonight. We call this degradation feature Selective Availability (SA). This will mean that civilian users of GPS will be able to pinpoint locations up to ten times more accurately than they do now. GPS is a dual-use, satellite-based system that provides accurate location and timing data to users worldwide. My March 1996 Presidential Decision Directive included in the goals for GPS to: “encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide; and to encourage private sector investment in and use of U.S. GPS technologies and services.” To meet these goals, I committed the U.S. to discontinuing the use of SA by 2006 with an annual assessment of its continued use beginning this year.

    The decision to discontinue SA is the latest measure in an on-going effort to make GPS more responsive to civil and commercial users worldwide. Last year, Vice President Gore announced our plans to modernize GPS by adding two new civilian signals to enhance the civil and commercial service. This initiative is on-track and the budget further advances modernization by incorporating some of the new features on up to 18 additional satellites that are already awaiting launch or are in production. We will continue to provide all of these capabilities to worldwide users free of charge.

    My decision to discontinue SA was based upon a recommendation by the Secretary of Defense in coordination with the Departments of State, Transportation, Commerce, the Director of Central Intelligence, and other Executive Branch Departments and Agencies. They realized that worldwide transportation safety, scientific, and commercial interests could best be served by discontinuation of SA. Along with our commitment to enhance GPS for peaceful applications, my administration is committed to preserving fully the military utility of GPS. The decision to discontinue SA is coupled with our continuing efforts to upgrade the military utility of our systems that use GPS, and is supported by threat assessments which conclude that setting SA to zero at this time would have minimal impact on national security. Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened. This regional approach to denying navigation services is consistent with the 1996 plan to discontinue the degradation of civil and commercial GPS service globally through the SA technique.

    Originally developed by the Department of Defense as a military system, GPS has become a global utility. It benefits users around the world in many different applications, including air, road, marine, and rail navigation, telecommunications, emergency response, oil exploration, mining, and many more. Civilian users will realize a dramatic improvement in GPS accuracy with the discontinuation of SA. For example, emergency teams responding to a cry for help can now determine what side of the highway they must respond to, thereby saving precious minutes. This increase in accuracy will allow new GPS applications to emerge and continue to enhance the lives of people around the world.

    Gianni
    Cedar Rapids, IA
    Posts: 2063
    #336999

    It’s a load. GPS is, right now, more accurate than it has ever been. Essentially the only errors are ionospheric delay, which is modeled and/or compensated by WAAS, and multipath/antenna blockage.

    Unfortunately, a handheld on the ice is probably one of the toughest conditions, due to multipath. You’re still probably within about 4 yards of your waypoint. If it’s one of those days where you need to be right in the trees, then the GPS will get you close, but the power auger and flasher will put you on the fish.

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