Re: [OSM-talk] High-Precision GPS Survey Equipment?
On 8/25/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hi all, Just to give a hint at what is possible, the company I work for flagship receiver (L1/L2 dual frequency) can achieve sub-cm accuracy for static observations when tied into a nearby reference station (or other receiver). Anyone know if the very high accuracy receivers can maintain their accuracy whilst on the move, in a car for example, or whether you'd need to be static or do frog-jumps from point to point? ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Tue, Aug 26, 2008 at 6:33 PM, Tim Waters (chippy) [EMAIL PROTECTED] wrote: On 8/25/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hi all, Just to give a hint at what is possible, the company I work for flagship receiver (L1/L2 dual frequency) can achieve sub-cm accuracy for static observations when tied into a nearby reference station (or other receiver). Anyone know if the very high accuracy receivers can maintain their accuracy whilst on the move, in a car for example, or whether you'd need to be static or do frog-jumps from point to point? ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk Here's how John Deere does it. I don't think it will do any good for interference from buildings though. http://en.wikipedia.org/wiki/StarFire_(navigation_system) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
[OSM-talk] High-Precision GPS Survey Equipment?
Hi list, Has anyone out there had any experience with the high-precision GPS survey equipment? While poking around on eBay yesterday I ran into some sub-meter and sub-decimeter precision GPS equipment. It was extremely expensive (USD$5000 - 15000), but it would be fun to try borrowing one of these units from the local university to get readings for some important places. -Ian ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Hi Ian, How much precision do you want/need? And apart from the fun of it, does it actually benefit OSM going to these lengths? If you were in Alberta I might be able to get some 'test time' on a couple of dual frequency units Mungewell. PS. Some of the Garmin units can be put into a 'test' mode where they spit out raw data, which can be post processed. But then you are limited by the crappy patch antenna and the quality of the receiver electronics. Hi list, Has anyone out there had any experience with the high-precision GPS survey equipment? While poking around on eBay yesterday I ran into some sub-meter and sub-decimeter precision GPS equipment. It was extremely expensive (USD$5000 - 15000), but it would be fun to try borrowing one of these units from the local university to get readings for some important places. -Ian ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Mon, Aug 25, 2008 at 11:02 AM, [EMAIL PROTECTED] wrote: Hi Ian, How much precision do you want/need? And apart from the fun of it, does it actually benefit OSM going to these lengths? If you were in Alberta I might be able to get some 'test time' on a couple of dual frequency units Well I was just thinking about the fun of it. The experience of using professional survey equipment and perhaps talking with a professional surveyor could benefit OSM perhaps. Alas, I'm in Wisconsin, just out of reach of Alberta. Thank you though! ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Mon, Aug 25, 2008 at 4:02 PM, [EMAIL PROTECTED] wrote: Hi Ian, How much precision do you want/need? And apart from the fun of it, does it actually benefit OSM going to these lengths? My fairly accurate Garmin 60CSx is still wildly inaccurate when I position myself at the corner of a building and try to measure its dimensions since the building and the surrounding blocks most GPS signals. So more accurate surveying equipment would for one thing be more useful in getting data of regular quality in areas where there's bad reception. There's also the whole use case of mapping things with 5m accuracy where most GPS units start being very inaccurate. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Hi, My fairly accurate Garmin 60CSx is still wildly inaccurate when I position myself at the corner of a building and try to measure its dimensions since the building and the surrounding blocks most GPS signals. What if you had a very light bluetooth GPS mouse and strapped it to a helium-filled baloon, you know, the toy shop/fun fair variety, then let it slowly ascend tied to a light yarn until you're at the top of the building... ;-) Bye Frederik -- Frederik Ramm ## eMail [EMAIL PROTECTED] ## N49°00'09 E008°23'33 ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Just to confirm: GPS position is calculated from signals received from satellites: if all satellites give you the time and their position, by calculating the difference of time, you get the difference of distance to them, and consequently the position. If the signals are reflected on walls, their distance from satellite may increase by 10 or 20 meters, or even more. So there is no way, in such conditions, to get a precise position, except by waiting to have all signals in direct view. High precision GPS have highly accurate clocks, so that they can calculate precisely the difference of time. Possibly, they can decide to neglect some measurements out of range (if 5 satellites give one position and a 6th one a different position). But you will not get a meter-accuracy with GPS around buildings. Another way to increase accuracy MAY BE to add an acceleration sensor, that will give you your position compared to one reference point (because a GPS in open-space can give you a good accuracy after some time). - Mail Original - De: Ævar Arnfjörð Bjarmason [EMAIL PROTECTED] À: [EMAIL PROTECTED] Cc: osm talk@openstreetmap.org Envoyé: Lundi 25 Août 2008 19:22:17 GMT +01:00 Amsterdam / Berlin / Berne / Rome / Stockholm / Vienne Objet: Re: [OSM-talk] High-Precision GPS Survey Equipment? On Mon, Aug 25, 2008 at 4:02 PM, [EMAIL PROTECTED] wrote: Hi Ian, How much precision do you want/need? And apart from the fun of it, does it actually benefit OSM going to these lengths? My fairly accurate Garmin 60CSx is still wildly inaccurate when I position myself at the corner of a building and try to measure its dimensions since the building and the surrounding blocks most GPS signals. So more accurate surveying equipment would for one thing be more useful in getting data of regular quality in areas where there's bad reception. There's also the whole use case of mapping things with 5m accuracy where most GPS units start being very inaccurate. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Mon, Aug 25, 2008 at 05:22:17PM +, Ævar Arnfjörð Bjarmason wrote: My fairly accurate Garmin 60CSx is still wildly inaccurate when I position myself at the corner of a building and try to measure its dimensions since the building and the surrounding blocks most GPS signals. So more accurate surveying equipment would for one thing be more useful in getting data of regular quality in areas where there's bad reception. I recently spoke with someone who's job it is to measure newly laid cables and conduits in my hometown. He says even the professional GPS's they have will not fix (accuratly enough) a lot of times. Around buildings and under trees they still resort to measuring distances from a point where they do get a fix and then project the points (their gear does this nearly automatically for them though). Another thing : the high precision GPS gear comes with an (expensive) subscription for providing the highest accuracy... cu bart ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Mon, Aug 25, 2008 at 5:33 PM, Frederik Ramm [EMAIL PROTECTED] wrote: What if you had a very light bluetooth GPS mouse and strapped it to a helium-filled baloon, you know, the toy shop/fun fair variety, then let it slowly ascend tied to a light yarn until you're at the top of the building... ;-) Sir, I wish to subscribe to your newsletter. :) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Hi I use normally a EGNOS/WAAS submeter DGPS, often for OSM mapping. :-) My DGPS run really well only in optimal conditions (no satellite obstruction, multipath, etc.), but I observed that the performance in a urban environment is normally lower than a normal bluetooth GPS based on a Sirf III or a MTK chipset. I think that one of the keys of these cheaper GPSs are the better sensitivity than the most expensive DGPS, as well as the algorithm for calculating the position (myDGPS uses also carrier for decoding the signal). Bye Alberto ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Ævar Arnfjörð Bjarmason wrote: Sent: 25 August 2008 6:22 PM To: [EMAIL PROTECTED] Cc: osm Subject: Re: [OSM-talk] High-Precision GPS Survey Equipment? On Mon, Aug 25, 2008 at 4:02 PM, [EMAIL PROTECTED] wrote: Hi Ian, How much precision do you want/need? And apart from the fun of it, does it actually benefit OSM going to these lengths? My fairly accurate Garmin 60CSx is still wildly inaccurate when I position myself at the corner of a building and try to measure its dimensions since the building and the surrounding blocks most GPS signals. So more accurate surveying equipment would for one thing be more useful in getting data of regular quality in areas where there's bad reception. The way surveyors get around this problem (yes even the best GPS systems cant see around corners) is to take 8 waypoints by sighting down the edge of a building (2 points for each side). You can then draw the shape where the lines intersect. This is how the Ordnance Survey do it for instance (using an optical square to improve accuracy). There's also the whole use case of mapping things with 5m accuracy where most GPS units start being very inaccurate. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.6.7/1632 - Release Date: 25/08/2008 7:05 AM ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
On Mon, Aug 25, 2008 at 9:44 PM, Andy Robinson (blackadder-lists) [EMAIL PROTECTED] wrote: The way surveyors get around this problem (yes even the best GPS systems cant see around corners) is to take 8 waypoints by sighting down the edge of a building (2 points for each side). You can then draw the shape where the lines intersect. This is how the Ordnance Survey do it for instance (using an optical square to improve accuracy). This is what I generally do when I need to survey buildings but it can get hard in some situations when there are buildings everywhere and you can't find a good point to do even this. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] High-Precision GPS Survey Equipment?
Hi all, Just to give a hint at what is possible, the company I work for flagship receiver (L1/L2 dual frequency) can achieve sub-cm accuracy for static observations when tied into a nearby reference station (or other receiver). The data is post processes to give the most accurate results. Unfortunately this level of precision is not cheap, and the math behind all this is far above my head... Cheers, Mungewell. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
