Anyone Help Test a GPS App?

**ukchris** · 03-14-2004, 07:52 AM

Is anyone on the move that could run an app hooked to their NMEA GPS and tell me if it captures speed / heading or not? Working with GPS data at a desk really is a pain in the rear. I know there are test apps out there thatr spew GPS data, just haven't got that far yet.

Somehow every file I make zips to about 220k so I can't attach it, I can mail it to anyone who'd like to help though. It simply reads the GPS data and displays the lat/long/speed and course. If you capture data with a valid speed and heading I'd like to know:

a) Was it shown in the first or second speed/heading box, or both?
b) What was a sample of a speed and a course it displayed?
c) Can you cut an paste the text from the lower window and mail it to me, with this and (b) I can check I am parsing the NMEA strings correctly.

If you're up for trying it PM me an email address and I'll send you the app, unless I can get my attachment size increased to maybe 250k...?

Chris.

**SilentAdmirer** · 03-14-2004, 09:17 AM

Hi chris,
I think I could help you with that. I will be trying my GPS application on my laptop this week. I sure could run urs too. Also along with the message is a small GPS log I created to test my app.
Its from germany.Hope it helps

Regards
Satish

**ukchris** · 03-14-2004, 09:43 AM

Originally Posted by SilentAdmirer

Hi chris,
I think I could help you with that. I will be trying my GPS application on my laptop this week. I sure could run urs too. Also along with the message is a small GPS log I created to test my app.
Its from germany.Hope it helps

Regards
Satish

Thanks Satish, I was kind of looking for someone who is heading out soon, I'll be out and about later and can do it then, thanks though.

What are you developing? What tools are you using?

I'm aiming to display the GPS data, speed, heading etc. but what interests me more is to tie the speed to the volume, I'm going to try to compensate for speed noise by increasing the volume dynamically (and reducing it as you slow down).

I'm finding clear documentation on the NMEA sentences hard to find. I'm getting the LAT/LON from $GPGGA as well as the altitude. Not sure if I should use $GPVTG or $GPRMC for heading and speed, I don't know which is appropriate yet as I have only tested at a standstill!

Chris.

**hijinks21** · 03-14-2004, 09:56 AM

I did the GPS for ME using mappoint. There's a bunch of websites out there that descirbe the different NMEA strings your reciever will send. I used two and i know the GPRMC was one of them. Your reciver should be pretty acturate with speed. WHat i did with GPS and speed is as you speed up the map starts to zoom out and as you slow down it zooms back in

**SilentAdmirer** · 03-14-2004, 10:25 AM

I am almost done developing a navigation system using Mappoint for turn-by-turn instruction. I use the speed for zoom in and zoom out and the warning distance.

Regards
Satish

**ukchris** · 03-14-2004, 10:53 AM

Originally Posted by SilentAdmirer

I am almost done developing a navigation system using Mappoint for turn-by-turn instruction. I use the speed for zoom in and zoom out and the warning distance.

Regards
Satish

Just been for a spin. Looks like GPGGA is fine for LAT/LONG/ALT and GPVTG for Speed and Heading. I need to do some checking as I was just using native data so I need to convert to MPH to ensure I'm getting an accurate reading but it looks good. I'll try and clean it up later and have some sort of test app if people want to experiment.

This also relies on having access to the NMEA data of course, I'm using a virtual serial port splitter so I have my GPS available from four virtual COM ports at the moment. Are you guys accessing it directly (and therefore unable to use the same port with a GPS) or are you accessing it by other means (via MapPoint?).

Chris.

**frodobaggins** · 03-14-2004, 02:29 PM

This may help:

http://directory.google.com/Top/Scie...rds/NMEA_0183/

**SilentAdmirer** · 03-14-2004, 03:01 PM

I am directly accessing the serial port for the GPS data.

**ukchris** · 03-14-2004, 03:30 PM

Originally Posted by frodobaggins

This may help:

http://directory.google.com/Top/Scie...rds/NMEA_0183/

I've been using the first two from this list, although they are technically quite good it is still hard to determine which speed string to use etc. In the end I set up my app to display several and then pick which looks best. That's where I hit snafus as it's hard to test speed and heading while sat at my desk. I can get a fix by sticking my GPS on a stick out of the window, it is still stationary though.

I think I know have all the details I need, just need to pretty up the application. I can set the PC volume easily, I need to determine some sort of ratio though for speed to volume. Interested in opinions on this.

I'm thinking there will be a base threshold - you don't want zero volume when standing still - and a low speed threshold at which compensation cuts in. From there I think I should increase volume by a certain amount per unit of speed and allow that ratio to be customized - some cars are noisier than others. The volume is set from 0 - 100, I just need to come up with an algorithm to decide on the volume based on the speed.

Any thoughts welcome.

Chris.

**hijinks21** · 03-14-2004, 04:32 PM

you're want to increase it based on percent. So at a stop you increase it by 0% and say going 70 you increase it by 30% and the rest is just math. Generally you set the volume via 0-100. So if your standing still volume is at 50 and you are going 70. so we'd need to increase it by 30% so bring it up 30% of 50 which is 15 or so