OK I will be more specific. I've seen a few links this year, but I can't find them again. I have a few different Bluetooth GPS modules that work great, but I want to use them with my Uno. I'd like to find a small, cheap serial GPS. Good performance, accuracy, reliability when there are trees around like in the forest. I have a few small boards that work fine in the clear sky, but not all the time around trees or steep terrain. My goal is to be accurate within 50', 99% of the time. The other 1% may have too few satellites with a strong signal due to trees. To summarize I want the performance of the modern Bluetooth GPS modules, on a small board, with serial output. Anyone have any suggestions?
Wow, seems like GPS modules are just becoming commodoties anymore.
Is there a problem adding bluetooth module to the uno to talk to the bluetooth GPS?
Would it be so easy? It's a popular Globalsat brand from years ago. Seems like there's a BT driver on the PC?
I've been using the "ultimate gps" from Adafruit for a few months and I think it meets your requirements. It is available on a small breakout board or as a bare module. Based on the MTK3339 chipset, it has high sensitivity, low power (25mA), can do built-in logging, etc.
WOW looks great! Only a few more dollars than I expected to spend! Just a few questions first:
- Warm start 34 sec. Hot start 8s? Their cheaper modules have it.
- Can you access the RTC without "starting" the GPS?
- Can you read the internally saved data log with Arduino? I'm not referring to Locus or similar data logging.
- 10hz really? Or is it fake interpolated data like 2-years-ago-modules?
- 1.8m means what? What is your average horizontal position error when it's not moving for an hour?
- Since they are out of stock, where else can we buy it online?
I'd really appreciate your help so I don't make another mistake buying a unit that does not meet my needs.
I'll do my best to answer, but some of them you might want to ask directly in the Adafruit forums, their support team are very good about responding there.
1) If it has a clear view of the sky, it warm-starts very quickly, I'd be surprised if it took 34s. Hot start seems almost instant to me. Indoors it's slower of course. The only thing I have found is a complete cold start, indoors, can take forever (2hours or more). Especially the very first time you power it up, it's got no saved references at all, so you want to be outdoors or give it a clear view. After that, it is brilliant.
2) Unfortunately not. I had tried making use of the RTC but basically the way it works is once the GPS has gotten a time signal from a sattelite, it will continue to keep time even without any sattelites in view. It outputs the time in its standard NMEA sentences (GGA and RMC) but I don't think there's any other special way to utilize it. There is also a PPS output but I haven't played with that (yet - will be using it in my next project.)
3) You can access the log data but I do not know if it can be parsed directly on an arduino. You send an NMEA sentence to the gps and it outputs all the log data via serial, but I don't know if the format is straightforward. Adafruit has a web page that can translate it to different formats, so I don't believe it is a proprietary format, just not immediately obvious to me what the formatting is.
4) It can do 10Hz for real, but I think it's limited to just one sentence (RMC I believe) at that rate. (I've only used it at 1Hz so I haven't played around at the higher frequency)
5) There is a bit of horizontal drift when you're stationary, but you can lock that out. There's a command where you can set the minimum track velocity, eg. if it's moving less than N meters per second, ignore the tiny movements. I have it set to 0.6m/s and basically when I'm not moving the Lat/Lon don't drift.
6) Sadly I have not found anyone else who stocks these. I've been waiting 2 weeks so I'm hoping they'll be back in stock very soon.
Thanks great answers! Can we talk a little more about 5) ?
If you disable that feature how much does it drift over time when it's not moving?
You can test this by picking the first reading as correct, after it has all satellites locked in an open field. Then you can see how many feet/meters each sentence is from that "correct" reading. What is that distance on average?
might be late but thought of posting this because I just about to getting this on Friday, found it on adafruit, but bought on ebay for much cheaper,
UP501 Breadboard-friendly 66 channel GPS module w/10 Hz updates - MTK3329 https://www.adafruit.com/products/660
manufacturer specs can be found here: http://www.fastraxgps.com/products/gpsantennamodules/500series/up501/
will give my experience with it on soon.
Looks like it might meet my needs for less $. But it doesn't have those cool new features that the Ultimate does. Looking forward to hearing your experience...
I used the UP501 for a couple months (before I got the 'ultimate' one) and it is a good solid unit. I believe it uses the MTK3329 chip.
I found it very sensitive, very fast to get a fix. It can do up to 10Hz output. And with the 0.1" pin spacing it is a lot easier to work with than some of the other modules. The only reason I stopped using it was that my application was portable/wearable and the MTK3339-based unit used a lot less current, and had sleep modes I could implement with software.
Apart from that (and the logging function), the two modules are very comparable in performance and function.
Here is a bit info about UP501 from ebay.
Its good in every aspect comparing to my modified good old Globalsat BT-359 and awesome when comparing to the used 16 dollar crap I ordered from HongKong which is not usable any more.
The only thing it concerns me is its satellite fix time is not that great as BT-359, may be just because every time cold start because of lack of backup battery. Anyway it managed to get the fix within 2 minutes, while BT-359 does it just within its first minute !.
Also I’m not very pleased with the bare packaging it arrived because its back metal plate got bit chopped when it arrived, might be due to some stamping process right on top of it.
I’ll attach a picture of it to compare its size and u to see what happened to its back.
Still not back in Stock... I'm waiting...