GPS tracking with Iphone 4

[bloopbloob]

Just wondering if anyone uses their Iphone 4 to record their fishing hotspots via GPS? I'd like to start doing this, but not sure how to go about this or what app to try out. I just want something that will basically record where I set points, then be able to view it later on a map to find the exact spot again, kind of like how google maps works when you get directions...

[bubbles]

Hey bloopbloob

i use the google maps app on my blackberry.

well your on the ice or in the boat you can go into it and mark a point where you are and it saves.

http://www.google.com/mobile/maps/

works pretty good.

[Ryancskor]

Navionics! Works good but pricy at $15

[Photoplex]

Dropping pins in the built in Google Maps is fine, but you must have a data/network signal to see the actual map. Something worth knowing is this: you can still drop pins in the app without a data/network signal. The pin stores your GPS location coordinates. When you get back into cell coverage, and the map loads, you'll see where you were.

A better solution is the Navionics app. This will give you bathymetry data (depths etc), and it will still show you the maps out of cell/data coverage.

[Tungsten]

Do you find the navionics positioning to be correct on the phone? Seems when I'm looking for specific structure it's a ways off. At cold lake I was marking 120ft and navionics had me in 80-90ft.

[iliketrout]

Is there a list of AB lakes that I can look at before I buy it? This could be quite useful!!

[Photoplex]

Originally Posted by Tungsten

Do you find the navionics positioning to be correct on the phone? Seems when I'm looking for specific structure it's a ways off. At cold lake I was marking 120ft and navionics had me in 80-90ft.

Which iPhone? It won't be the app - it'll be the GPS receiver in your phone causing the problem.

Originally Posted by iliketrout

Is there a list of AB lakes that I can look at before I buy it? This could be quite useful!!

How many Navionics Apps are available in App Store?
A. There are 7 Navionics Marine Apps in the App Store. Marine&Lakes: USA, Marine&Lakes: USA&Canada, Marine: Carib&S.America, Marine: Europe, Marine: UK&Holland, Marine: Denmark&Greenland, Marine: Australasia&Africa. All Apps provide with screenshots showing the coverage area in iTunes.

I'm assuming it's the same list of maps as in the SD card for sonar devices - if so, here you go for the Canada maps.

[Tungsten]

Here ya go. Fairly comprehensive.

http://www.navionics.com/LakeList_HM...asp?RegionID=5

[Tungsten]

Sorry that was the platinum maps.

Think they're the same but here's the mobile list.

http://www.navionics.com/Charts_Mobi...AB&Area=Canada

[Tungsten]

[QUOTE=Photoplex;845479]Which iPhone? It won't be the app - it'll be the GPS receiver in your phone causing the problem.

I have the iPhone 4. Using google maps the gps seems to pinpoint me quite well.

[nicemustang]

Originally Posted by Tungsten

Do you find the navionics positioning to be correct on the phone? Seems when I'm looking for specific structure it's a ways off. At cold lake I was marking 120ft and navionics had me in 80-90ft.

This is normal with the navionics maps. Just adjust your offset so the depths are right. This is because of flucuations in the lakes, i know all the southern reservoirs are off depending on water level.

[iliketrout]

Thanks guys. The list is decent but I notice some glaring omissions (Which is surprising since Birch and Beaver are on the list):

CVR
McGregor
Badger
Newell
Little Bow

Now that I think about it, I seem to remember that some guys who bought the chip for their fish finders had the same complaint.

Oh well, can't really go wrong for $15.

[nicemustang]

Yep, its because the county's won't release the topo maps to them for whatever reason.

[Photoplex]

Originally Posted by iliketrout

Thanks guys. The list is decent but I notice some glaring omissions (Which is surprising since Birch and Beaver are on the list):

CVR
McGregor
Badger
Newell
Little Bow

Now that I think about it, I seem to remember that some guys who bought the chip for their fish finders had the same complaint.

Oh well, can't really go wrong for $15.

Yup - kind of funny how those you mentioned aren't there... yet Chestermere is?!

There is a lake request link on their site somewhere. If enough people suggest those missing major bodies, maybe they'll get it done this summer.

[Photoplex]

Originally Posted by nicemustang

Yep, its because the county's won't release the topo maps to them for whatever reason.

I heard from a friend that the AB provincial government won't allow commercial operations to map their lakes - and thus Navionics has to rely on the government maps... what you're saying seems to lend credence to that.

Why though?!

[nicemustang]

Well this is just speculation but....certain people with power in the county's are big fisherman and don't want to help out a corporation that could potentially hurt their fishery.

If it wasn't for a lot of time spent on a calm perfect condition day at newell one summer, I would know general from the lake map where the humps and holes were but not exactly....GPS is a wonderful thing now but even then it can be tricky to find what you are looking for. Finding a 40x40 foot hump in the middle of a lake that is 16,000 acres isn't that easy, but if I had it on my navionics chip it would take seconds.

[DarkAisling]

Originally Posted by Photoplex

Which iPhone? It won't be the app - it'll be the GPS receiver in your phone causing the problem.

Before I disagree with you, I feel that I should state my disagreement isn't about "one-up-manship" (I've been accused of that in the past with regards to a post on this forum). I've been in geomatics for 10 years (a cartographer for eight of those), and I've been involved in virtually every aspect of data collection, processing, and representation. I simply want to ensure that AOFers have a clear understanding of how maps and location finding devices work.

From what Tungsten has posted, it sounds as if it is only his z value that is off.

X=Longitude
y=Latitude
z=Vertical

Providing his x and y are correct, his iPhone has nothing to do with determining the depth. The issue is either:
a) the Navionics map, or
b) the device he is using to measure the actual depth.

If I was standing beside him in the boat I could probably figure out the cause of the error pretty quickly, but I'm sitting behind my desk in Calgary and Slave is frozen solid.

I'm definitely leaning towards an issue with the map.

There could be a number of reasons why the depth is off, but I'm guessing it is a combination of the water level and the grid spacing used in the collection of the bathymetric data: mostly the grid spacing (the distance between the points where the x,y,z was collected) as I don't think Slave fluctuates a huge amount. The are a wide range of processing errors that are possible, too.

I've just downloaded Navionics ($35 for the iPad version), and there is no metadata provided that gives me any clue as to the quality of the data. It is most likely compiled from a wide range of sources, using various techniques, collected over the course of several decades.

I'm thinking (from messing around with Navionics for less than 1/2 an hour), that Navionics is phenomenal as a general guide: it will give you a very good idea what the structure is like (where the holes, channels, etc. are), but the depth data is a bit sketchy.

I'm looking at Travers, which has a huge fluctuation in water level. If an area has a depth of 23' (according to the Navionics map) below waterlevel, what was the waterlevel when that depth was recorded? I much prefer to see measurements AMSL (above mean sea level) as those have nothing to do with the actual water level (they are topographic contours, versus bathymetric, basically).

Now, if Tungsten's x and y are off, that is his phone. He would need to confirm his x and y with an autonomous (true) GPS.

I've been digging into Apple's AGPS (assisted GPS) chips for around a month now (iliketrout can confirm this . . . I'm not exaggerating), and I finally (as of yesterday) have a 100% definitive answer as to how they work.

AGPS chips are not like autonomous GPS chips. AGPS chips only communicate with cell towers. The cell towers (which are communicating with the satellites) provide the location to the AGPS chip in the device.

So, AGPS is not "true" GPS. However, it is often faster and more accurate than autonomous GPS chips (which communicate directly with satellites) . . . so it certainly has its benefits.

If you loose your connection to a cell tower, your AGPS will not function. But! (This is the part that has had me scratching my head) AGPS will function off of a very weak signal: weaker than your phone will register as a "connection" on your screen. Therefore, it could appear that you don't have a connection, and you can't make a call, but the device is still communicating with the tower well enough to return location data.

In the event you do completely loose connectivity, an external autonomous GPS receiver (requires a clear view of the sky, and communication with a minimum of four satellites) can be hooked up to your iDevice.

The most cost effective that I've found is this:
http://bad-elf.com/products/gps/

Canadians have to order from Ebay, and it was around $160 all in. Mine isn't here yet, so I've yet to actually test it.

What I really want is this one of these "Pathfinder" babies:
http://www.trimble.com/mappingGIS/GNSS-Receivers.aspx
But, at 3k to 11k , I'll "settle" for the Bad Elf.

Some Navionics screen shots of Travers:

[FishBrain]

I use MotionX GPS as my program. You can mark points and email them and use google to view. Good program, much better now that I am starting to use it more

[Photoplex]

Originally Posted by DarkAisling

From what Tungsten has posted, it sounds as if it is only his z value that is off.

X=Longitude
y=Latitude
z=Vertical

Quick reply before I dash out the door to work.

Initially, his post made it sound like his X & Y were out. That would be the fault of the device (only locked into cell triangulation, and not yet WPS or GPS).

Then he elaborated, and it became clear that it was a Z axis issue. GPS devices also calculate altitude. It is perfectly possible that the device is miscalculating his height above sea level...

...then I remembered that the Navionics stuff is a simple map overlay - there's no magic going on calculating the delta between your actual GPS determined altitude, and the internal maps understanding of how how much space is still below you.

[Photoplex]

Originally Posted by DarkAisling

I've been digging into Apple's AGPS (assisted GPS) chips for around a month now (iliketrout can confirm this . . . I'm not exaggerating), and I finally (as of yesterday) have a 100% definitive answer as to how they work.

AGPS chips are not like autonomous GPS chips. AGPS chips only communicate with cell towers. The cell towers (which are communicating with the satellites) provide the location to the AGPS chip in the device.

So, AGPS is not "true" GPS. However, it is often faster and more accurate than autonomous GPS chips (which communicate directly with satellites) . . . so it certainly has its benefits.

If you loose your connection to a cell tower, your AGPS will not function. But! (This is the part that has had me scratching my head) AGPS will function off of a very weak signal: weaker than your phone will register as a "connection" on your screen. Therefore, it could appear that you don't have a connection, and you can't make a call, but the device is still communicating with the tower well enough to return location data.

In the event you do completely loose connectivity, an external autonomous GPS receiver (requires a clear view of the sky, and communication with a minimum of four satellites) can be hooked up to your iDevice.

That's not strictly true. iPhones do use satellite GPS triangulation as a 3rd tier. Here's a quick breakdown of how they work:

The technology used in Apple location service devices - uses 3 forms of location triangulation.

• Firstly, and most quickly - Cell Tower location. This is the quickest and dirtiest way for the phone to get a lock on where you are. It knows which cell tower you are connected to. It knows the location of it. It knows the transmitting radius of it. Thus, it quickly knows you are within X km of an exact location.
  
• Next, it uses a technology called WPS. WiFi Positioning System. This uses an internal database of WiFi network MAC addresses, with a LatLong marker stored for each one. There are companies that send vehicles on a daily basis to drive around our cities (North America, Europe etc). They have WiFi receivers in the car, and a GPS. When it drives down your street - it collects the MAC addresses of all the WiFi networks it finds, and tags them with a LatLong marker. This database is in your phone. When your phone finds a wifi network near it with the MAC address 00:11:22:33:44:55, it looks it up, and knows where you are. The accuracy is usually around 200m or less, as this is the range of most WiFi networks.
  
• Lastly - the device uses an actual GPS chip to triangulate your position using satellites (usually 3?).

This is why if you are inside a tall concrete building, your iPhone will firstly locate you with a large radius of usually 1-5km. Wait a few moments, and that suddenly changes to a much smaller radius of ~200m - as it detected the wireless networks near you and got a better lock.

If you walk outside of your tall building, you will notice it suddenly correct itself and lock you in to a radius of approx 10m.

The reason you can buy external add-on GPS receivers for the iPhomne (like the Garmin etc) is to improve accuracy. The iPhone builtin GPS chip can only handle a limited number of simultaneous satellites, and thus the accuracy is limited to a range of x meters. These addon devices are capable of handling many more simultaneous satellites (in Garmins case I believe it's 12), improving accuracy down to 2m or less.

[nicemustang]

Dark...i'm confused slightly, please clear something up. Why does one need to buy a bad-elf program? For $160...couldn't you just use a handheld GPS? What's the benefits of this program for use on the ipad?

[DarkAisling]

Originally Posted by Photoplex

Lastly - the device uses an actual GPS chip to triangulate your position using satellites (usually 3?).

I would really like to know who told you that, or what draws you to that conclusion. I've been told three times (by three separate Apple "geniuses" . . . two phone calls and one in-person chat) that the iDevices absolutely do not have an autonomous GPS chip (typically requires 4 sats). The product specs don't indicate an autonomous chip, either. I've been knocking myself out trying to understand why iliketrout's iPhone is solving for location when according to the specs it shouldn't be (the answer being the required signal strength, as per my previous post).

FYI: I would LOVE to know that the iDevices do have an autonomous GPS chip. If that's the case I'll return the Bad Elf receiver when it gets here and be $160 richer. However, I have been specifically told be three different Apple employees that they don't.

[Photoplex]

Originally Posted by DarkAisling

I would really like to know who told you that, or what draws you to that conclusion. I've been told three times (by three separate Apple "geniuses" . . . two phone calls and one in-person chat) that the iDevices absolutely do not have an autonomous GPS chip (typically requires 4 sats). The product specs don't indicate an autonomous chip, either. I've been knocking myself out trying to understand why iliketrout's iPhone is solving for location when according to the specs it shouldn't be (the answer being the required signal strength, as per my previous post).

FYI: I would LOVE to know that the iDevices do have an autonomous GPS chip. If that's the case I'll return the Bad Elf receiver when it gets here and be $160 richer. However, I have been specifically told be three different Apple employees that they don't.

So called Apple "geniuses" are morons. They attended a 2 day course on apple products. They are not an authority. As explained - the iPhone chip and antenna does locate using satellites (as a 3rd tier) - but it doesn't handle a lot of simultaneous satellites, and thus accuracy is not high. Apple never designed it to be an accurate cartographic device - it was designed to allow its users to locate themselves to within a handful of meters if they were lost.

There are many, many articles online on how the iPhone location services work. One example

Your confusion is on what the A in AGPS means. Assisted means that when the device is unable to detect a satellite signal (you're in a big concrete building) it uses other techniques to find out where you are (namely cell and WPS). You in-car GPS does not have that luxury. Take it into your condo, and you get the irritating woman bleating "NO SATELLITE RECEPTION" over and over.

The iPhone 3G, iPhone 3GS, and iPhone 4 models use A-GPS -- or "Assisted GPS" -- which in basic terms accesses an intermediary server when it is not possible to connect directly via satellite -- indoors, for example -- and this server provides the nearest satellite with additional information to make it possible to more accurately determine a users position.

Apple explains that the iPhone 3G, iPhone 3GS, and iPhone 4 also use "wi-fi hotspots and cellular towers to get the most accurate location fast" when GPS is not the most convenient method of location detection.

Does that help?

[DarkAisling]

Originally Posted by nicemustang

Dark...i'm confused slightly, please clear something up. Why does one need to buy a bad-elf program? For $160...couldn't you just use a handheld GPS? What's the benefits of this program for use on the ipad?

The Bad Elf (autonomous receiver) plugs directly into the iDevice, and will show one's location on the mapping software on the iDevice. Handheld GPS units can not presently be connected to an iPad (or iPhone) . . . well, there are some bluetooth options for connectivity to an external GPS receiver, but they're finicky and more pricey. The Bad Elf should be very simple to use: when the device's other location services don't work.

Whether or not there are advantages to using an iDevice over a traditional hand held GPS depends entirely on the software one is using (and I really like a lot of the navigational software I've been testing on the iPad).

[DarkAisling]

Originally Posted by Photoplex

Your confusion is on what the A in AGPS means.?

No, I'm not confused.

[Photoplex]

Originally Posted by DarkAisling

No, I'm not confused.

I'm not getting into a p!ssing contest with you mate. iPhones use Cell, WPS, and GPS for location services.

[iliketrout]

DarkAisling and I (well, mostly DarkAisling) have been working on using a couple existing apps and the SRD maps to make our own "Navionics" data for some lakes. Travers has been our test subject.

As anyone can attest, most spots on Travers have no cell phone signal. Which is to say that there is not enough signal to use the phone. That being said, I have never lost my GPS out there. Same goes for when I'm hunting. I have never lost my GPS signal.

So, with assisted GPS, I can get extremely accurate positions on:

Google Earth
Motion X GPS
Avenza PDF Maps

I don't know how it works. But I assume it is running off the very weak cell signal that I am getting...

[Photoplex]

Originally Posted by DarkAisling

AGPS chips are not like autonomous GPS chips. AGPS chips only communicate with cell towers. The cell towers (which are communicating with the satellites) provide the location to the AGPS chip in the device.

Originally Posted by Photoplex

Your confusion is on what the A in AGPS means.

Originally Posted by DarkAisling

No, I'm not confused.

Assisted GPS, generally abbreviated as A-GPS or aGPS, is a system which can, under certain conditions, improve the startup performance, or TTFF (Time To First Fix) of a GPS satellite-based positioning system. It is used extensively with GPS-capable cellular phones as its development was accelerated by the U.S. FCC's 911 mandate making the location of a cell phone available to emergency call dispatchers.[1]

[Photoplex]

Originally Posted by iliketrout

I don't know how it works. But I assume it is running off the very weak cell signal that I am getting...

No - as explained, AGPS has nothing do with whether it communicates with a satellite or not (and in the case of the iPhone, it most certainly does use satellite for GPS location).

It's a system to a) allow you to locate yourself when you are not able to receive a satellite signal and b) to more quickly locate yourself.

Have you ever left your car GPS off for a long time, and then turned it on? Have you ever driven a long way, and then turned it on? Notice how long it takes to get an initial lock on you? That's because it has to start over - figuring out which satellites are near you, triangulating you from scratch. To the device - you could literally be anywhere in the world, and it needs to start from scratch.

With AGPS, the device contacts a cell tower, asks where it is, it responds, and the device knows exactly which 2/3 satellites to look out for.

[DarkAisling]

Sorry . . . images didn't work for some reason.

Originally Posted by iliketrout

I don't know how it works. But I assume it is running off the very weak cell signal that I am getting...

That is the answer that our ALS/CLS gave me yesterday, and as his knowledge far exceeds mine when it comes to GPS receivers, I'm taking his word for it . . . unless we definitively determine otherwise when we're out testing the data and the devices (once I chew through the straps that have me bound to my desk, that is ).