Android App for Speed?

[ASMOLEY]

Does anyone know of an Android app that will get accurate speeds to tenth on a mile? I run the Navionics app but the speed is really irregular while running at trolling speeds (<2 mph)sometimes its on my screen and other times it disappears. I've tried some GPS speedometers but none will read out tenths of a mile. I've tried different model phones and they all work the same.

Maybe it's just a limitation of smartphone GPS?

[Valv]

I have GPS Status & Toolbox and it has the 10th of a mile. I use it to check speedometers accuracy.

[McGurk]

Maybe it's just a limitation of smartphone GPS?

This. Even if it reads to the tenth, I'd be suspect of its consistency, and therefore accuracy. Thats the nature of commercial grade gps.

[ASMOLEY]

I have GPS Status & Toolbox and it has the 10th of a mile. I use it to check speedometers accuracy.

Valv, I've been trying to get this app to read speed into 10th of a mile but I can't find any options. It will read distance into 10th of a mile but not speed. Am i missing something?

The Navionics app will read into 10ths of a mile but not consistently at trolling speeds <2mph.

I might just have to bring the Garmin with for speed, phone for navionics lake maps, and the Lowrance X67c for sonar... Starts to make the new models seem more attractive I just with the price was the same!

[CJH]

This. Even if it reads to the tenth, I'd be suspect of its consistency, and therefore accuracy. Thats the nature of commercial grade gps.

The margin of error is probably too great to get that accurate of a reading. Remember, current GPS has about a 10ft margin of error, depending on device and who you believe. Gen III GPS satellites are supposed to come online around 2014 and should decrease that margin of error down to 1ft and have a stronger signal for easier acquisition, especially in places with lots of trees or tall buildings.

[Wish-I-Were-Fishn]

Will our current equipment work on the gen 3?

[McGurk]

Bear with me, you might learn something about one of my favorite tools.

To read to the 10th of a mile (NOT miles per hour, but distance) means that you need to be within a 528 ft radius, and most commercial GPSr's are able to get within a 30 ft radius. Sometimes even better, but again I'd be suspect of exactly how precise that it thinks it is. Don't get me wrong; I love mine and use them often, but I understand the limitations of them. I understand the fact that they will not navigate you repeatably to be on top of an exact marked spot, except by pure luck and coincidence, but they will get you close.

Do a little test yourself sometime. In the morning, walk to and and physically mark a spot on the ground in an wide open area that you get good reception. Now mark a waypoint on your handheld after standing on top of you marked spot. You can even "average" a number of readings if you are so inclined to try to tighten up your coordinates. Look into averaging if your GPSr is capable, as it can be a useful way to tighten up coords on a spot you go to often and want precision. You do need to stand absolutely still, and averaging will not work in a non-anchored boat.

Now, using your "go to" feature, use your GPSr to try to navigate to your waypoint, but only watch your GPSr and do not look ahead to the marked spot. When you feel comfortable with your reading and your arrival to your spot, mark that on the ground, and measure over to your previously marked spot. Do this on different days and different times of day to learn how your phone's or handheld's precision isn't as great as we all think it is. It is good, but not perfect, and you need to keep that in mind.

Regarding speed, what you are asking (MPH to the 10th) is feasible at higher speeds, but when going slow (less than 10 mph) you will not be able to reliably use your GPSr for speed. This is due to what you discovered in the above test, and that the GPSr will skip around 10 feet almost all the time. It is not calculating true miles per hour, but distance moved in a per second fashion (sometimes more often) and then extrapolated to be read in MPH. To move at a rate of 10 MPH, you need to move exactly 14.67 feet in one second (10*5280 ft/60 min/60 sec) consistantly, repeatably, and in a straight line. Asking your GPSr to do that is just not feasable at low speeds, and at high speeds the errors shrink as the distance covered is higher, and the calculations are more reliable to display mph.

The other thing you learned from the previous test is that your spot accuracy is never along a straight line, and not even along a flat plane. If you turn your elevation display on, you will see even more number jumping, as elevation is the weakest of the 3 dimensions to have a precise reading. This is from triginometry and acute angles. Sorry to go all math teacher on you!

[ASMOLEY]

Thanks for the lesson McGurk! Can't wait to get my hands on GenIII GPS...

[delcecchi]

Another exercise is to take your hand held gps on a walk of a couple miles and retrace route returning. Then look at display and max speed. A bike path or sidewalk is ideal for this.

When I did it, I found that i could walk almost 10 mph, and the paths did not overlay very well.

My boat GPS seems to be better with the speed, but I bet they are smoothing the data.

[CAMAN]

The main issue like Mcgurk said is the ping time. Smartphone programmers aren't expecting you to need to get to within a 1\10th MPH so the ping speed is set to 1 second or more intervals. Which means the GPSr talks with the satellite once a second. Some GPS's allow you to adjust ping speed to get highly accurate speed and location reading, the downfall is it kills the battery much faster. I am unaware of any way to adjust ping speed in smartphones, though it may be possible if you root but haven't looked into it.

[delcecchi]

GPS only receives from satellite. I guess they can save power by turning off the receiver or not doing the position calculations but the facts I posted above were for a Garmin handheld GPS.

[Scott K]

Another exercise is to take your hand held gps on a walk of a couple miles and retrace route returning. Then look at display and max speed. A bike path or sidewalk is ideal for this.

When I did it, I found that i could walk almost 10 mph, and the paths did not overlay very well.

My boat GPS seems to be better with the speed, but I bet they are smoothing the data.

You can walk 10 mph??

[delcecchi]

You betcha, verified by GPS, set to display max speed. Try it. Sometimes I apparently get on a roll and hit 14 mph.

[McGurk]

A 4 minute mile requires that you move 22 feet per second, or 15 miles per hour. According to your GPS you have a very impressive gait for walking! You might want to look into going to London and trying a walk-on tryout for the USA track team...