Does anyone know of a GPS module with a fast update rate?
1Hz is greatm but 10Hz would be better… 
My friends garmin GPS apparently can do updates at 100Hz, I’d love to get a module with that sort of performance!
Failing that, are there any undocument (or documented, but I didn’t find any) methods of getting a lassen iQ to update faster than 1Hz??
Hm,
I didn’t try it but if you run the module with the TAIP communications scheme you can quiery the position as often as you desire (says the datasheet - Page 200 ff.) Wonder what happens if you have a quiery frequency of 100 Hz - provided the serial connection is fast enough…
U-Blox has a 4Hz unit called the SAM-LS ($129.00 + connection cable?). It has an integrated patch antenna. I don’t know how well those patch antennas work. Can anyone give me some insight???
I think Garmin has a 5Hz unit for aroung $300.00
A while back, I talked to a sales rep from www.navtechgps.com and this is what he told me:
Jeff,
20Hz and inexpensive simply do not go together right now.
The Novatel OEM4s (L1), 20 Hz start at around $2000.00 for the board by
itself.
The Superstar II has a 5Hz output for $315.00. Again this is just the board.
Were you looking for a board level solution?
Novatel offers universities a buy one get one free policy but that would
have to be done through them.
Unfortunately they do not let their dealers offer the same discount.
Kind Regards,
Paul A. Witt
Navtech GPS Supply,
Sales and Customer Support
I’ve been using the UV40 with gained antenna for a couple of years now. I don’t like the 1Hz data rate, but it’s always balls on.
Jeff
www.gpsflight.com sells a very small 4Hz, 16 sat GPS module with RS232 interface for about $120.
I just ran into this module: http://www.garmin.com/products/gps185hz/ - 5hz but at $200 it’s a tad spendy. Also, as far as I can tell it’s not based off the SIRF III chipset, which is unfortunate.
I just ran across this: [Open-Source Software for COTS GPS Receivers (PDF, 2MB, master’s thesis). Not immediately applicable, but with open-source receiver designs, maybe some special-purpose GPS designs could be put together (e.g., ones concentrating on velocity or update rate instead of absolute position, or whatever.)](Portland State Aerospace Society)
Just because the update rate is faster, does that mean that the module is actually calculating a new position for each update?
Or does it only calculate a new position say every 1 second and continue outputing that same position every .1 seconds until another position is calulated every second?
I have always wondered this too, if a GPS with a refresh rate of 10 Hz is actually calculating and refreshing the position at 10 Hz or just spitting out the same position at 10 Hz. I am very interested to have this answered. Does anyone know?
Hummer,
Where I work, we use Ashtech GPS units (G12 - now phased out) capable of 10Hz update rates. The data is real, not repeated or interpolated. They’re expensive.
Javad also makes faster ones (20Hz), but as with any high-update-rate source, you end up with lots of data.
Depending on what you’re doing, it’s hard to justify such high data rates. If you’re doing a realtime display, you can’t visually process 10Hz data. If you’re logging data (say from a tracker) all but the fastest moving objects could be tracked fine with a lower update rate (and you end up with much smaller data files). The only slow objects I can see needing quick updates are UAV’s using the data for realtime control.
I imagine that if you tried quickly query one of the cheaper receivers (that is specified for a 1Hz output rate), you’d end up with the same position repeatedly between fixes.
-Matt
I seem to recall the Antaris has a 5 or 10 hz update rate, and it has very good “raw” measurements. The older board is only $120 from www.u-blox.com. The new Antaris, the LEA-4T is similar, but it has Sirf III-like tracking capabilities. It is available as a module, not a board, for $170. Despite the price, it is one of my favorites.
Usually, if you want the higher update rates you also want the extra precision from double differencing. It doesn’t make sense to get more frequent updates unless they are very accurate or unless you are going very fast.
Other choices include the Garmin gps18 with 5 hz update, and some of the Superstar II receivers.
Hi, I was wondering if anybody knew how small these units could get. I’m after something less than an ounce in size. I also would like it to have a fast refresh rate something in the area of five times a second or faster. I realize most GPS units have screens etc that make it difficult to be truly ultralight. I was wondering if there was just the GPS unit without any additional components or perhaps a passive gps unit that gets powered like a passive RFID chip and would relay its quickly refreshed positional data to a main terminal. Not sure if you can do this with GPS so I might have to look into RFID chips.
note that the GPS 3D position estimates have error statistics, with our without WAAS/DGPS, such that at high update rates, you will get a lot of “noise” in the data. In terms of statistics, interpolating would probably give about the same results.
RFID technology cannot estimate 2D location to any accuracy similar to GPS; most of RFID “RTLS” is merely estimating based on signal strength to several pre-defined immobile access nodes and ASSUMES that the RF propagation path losses are identical to those measured at some earlier time with a site survey. The alternative to this is time-difference-of-arrival (TDOA) which can be accurate but is high cost and vulnerable to multipath where the signal strength of the direct path can be less than some reflected (longer) paths, yielding incorrect position estimates.
To get really high rate fixes you need a fiber optic or other solid state gyro INS plus GPS plus a Kalman filter.
So I would also like to have a very fast refresh rate from a GPS, but I realize the problem with intense calculations with each refresh, and there may be another way for me…
Is there any units that would work well to externally trigger a locking of the GPS’s input signals very quickly, then the GPS can take as long as it wants to calculate?
Basically I want to take two readings about 3 seconds apart, but at specific times within at lease 0.1 second of knowing I need the reading (PIC processor is likely reading the GPS). I should be able to signal the GPS to take a reading faster than that, then it’d have 1+ seconds to calculate the result and respond before I’d need another reading, but again it’d have to be at a very specific time, triggered by the external PIC.
Or do all the GPS models out there calculate continuously at a pre-determined refresh rate?
Another but of info about my project is that I only care about relative readings (to eachother), not true position.
at a high rate of speed for the tracked entity, fixes this closely spaced in time may make sense. But the accuracy uncertainties in GPS are such that faster updates at vehicular speeds aren’t very useful, unless you are trying to average the heck out of samples for an immobile object and trying for high accuracy. If so, as do surveyors, look at RTK GPS.
relative readings: makes no difference. Each GPS location estimate is in error by an amount that can be almost purely random, or can be skewed. The circular error probability (CEP) is analyzed all to heck and gone for GPS, on the web. The errors do not form a circle for some error sources, such as “GDOP” where a lot of the sky is occluded. The main GPS error is from tropospheric propagation delay variations that change slowly (tens of minutes). This is what the Differential GPS corrections are for (DGPS), where the corrections are sent over landlines, Internet, private satellites, and lately by the FAA as WAAS - which most all newer GPS receivers can accept. With WAAS (see coverage for WAAS), the transmissions are from a geo-synch satellite and thus are more difficult to receive than are GPS satellites.