navigating off the grid: iPhone apps

[haven]

Here's a list of iPhone applications that combine GPS capability with downloaded topographic maps to help you navigate off the grid, that is, without any connections to cell phone towers or the Internet. (The iPhone 3GS has a built-in GPS that calculates its position using signals from satellites.)

EDIT: thanks to forum members who point out that the iPhone 3G also includes the built-in GPS. Both the 3G and 3GS use the same Infineon PMB2525 Hammerhead II assisted GPS chip and a short antenna that runs across the top of the phone.

In alphabetical order:

Accuterra
http://mobile.accuterra.com/

Fugawi GPS iMap
http://www.fugawi.com/web/products/fugawi_imap.htm

Gaia GPS
http://www.gaiagps.com/

iTopoMaps
http://www.itopomaps.com/

MotionX GPS
http://news.motionx.com/category/motionx-gps/

RouteBuddy Atlas
www.routebuddy.com
(can use USGS and UK Ordinance Survey maps)

Topos2Go
http://www.cynicsoftware.com/topos2go/

Topo Maps
http://chezphil.org/topomaps/

TopoPoint USA
http://www.ebranta.com/topopointusa.html

Did I miss any?

 

[haven]

One complaint I've read on other web sites is that the iPhone is not water resistant, so it's likely to be damaged when used in wet conditions. So finding a case that protects your iPhone from moisture and dust would be a wise investment.

A list is nice, but what we need is a comparison test of iPhone GPS apps in Overland Journal! Here's a list of features that might be used to compare GPS programs:

map library used: custom versus government?

cost of downloading maps?

areas mapped: USGS, Canadian provinces, elsewhere?

are maps included on DVD, or are they downloaded as needed

seamlessly view adjacent maps

add and remove waypoints

import tracks and waypoints

formats used to import and export waypoints

integrate with PC and/or Mac applications

zoom in/ zoom out

specify location in lat/long or UTM format

search for nearby points of interest
provide distance and bearing to specified point

record your progress as you travel

link photos to waypoints

combine tracks, waypoints with Google Earth photos

 

[dustboy]

I've used TopoMaps and I think it's very good, but I have questions about the sensitivity of the GPS chip, I've been in several situations where it wouldn't pick up a signal.

I'm curious to hear other people's experiences with these apps, it would be great to not need a standalone receiver.

 

[DaveM]

I've used TopoMaps and I think it's very good, but I have questions about the sensitivity of the GPS chip, I've been in several situations where it wouldn't pick up a signal.

I'm curious to hear other people's experiences with these apps, it would be great to not need a standalone receiver.

I'm not an iPhone user so I can't comment directly but my understanding is that it uses an augmented GPS signal which means that when in reach of cell towers it triangulates the singal to improve accuracy and location time. Away from any cell signal it will use the onboard GPS antenna which is not as sensative as most dedicated GPS devices.

 

[haven]

The original iPhone and iPod Touch don't have a true GPS chip (capable of receiving signals from nav satellites), but the iPhone 3GS does.

EDIT: the iPhone 3G also has the GPS chip.

 

[Mad Matt]

Im a big fan of Topo Maps on my iPhone 3GS. The quality of the USGS quads used by Topo Maps are the cleanest/sharpest I have ever used. Every time I have been out in the boonies, with no cell reception it has easily been as accurate as all of the hand held GPS units and rig based PC set ups. That said screen size makes a huge difference when viewing maps so a PC with an actual screen will win out every time in terms of usability.

 

[yubert]

I'm not an iPhone user so I can't comment directly but my understanding is that it uses an augmented GPS signal which means that when in reach of cell towers it triangulates the singal to improve accuracy and location time. Away from any cell signal it will use the onboard GPS antenna which is not as sensative as most dedicated GPS devices.

This is not accurate. The iPhone 3Gs uses a GPS chip designed by Global Locate (now owned by Broadcom) and licensed to Infineon, called the Hammerhead II. The sensitivity of the Hammerhead II is rated at -160 dBm.

Most current dedicated GPS devices use the SiRFstar III GPS chip which is rated at -159 dBm. To remain competitive, SiRF/CSR recently announced an updated GPS chip called SiRFstar IV which is rated at -163 dBm for tracking. However GPS devices using SiRF IV have yet to hit the market.

Additionally, the Hammerhead II GPS chip supports A-GPS (assisted GPS) which means it can use cell tower information to reduce the time it takes to acquire a satellite signal and position. Dedicated GPS devices do not have this feature except for WAAS.

Lastly, A-GPS does not need to triangulate with cell towers. The cellular networks already knows the position of each cell tower and it knows which cell tower your phone is connected to, which is the nearest tower, based on signal strength.

 

[fishbum]

Regarding sensitivity... those specifications of -160 to -163dBm should be taken with a grain of salt. It's likely that those numbers are under a very specific set of operating conditions, and not 'real world'.

Nobody would notice a difference of 1 dBm, you can gain or lose that much signal with a bad/good antenna layout.

Many manufacturers are reporting 'super sensitive' chipsets, but the reality is they all have the same laws of physics to work with, and they all have the same satellite constellation to work with. Its more of a marketing game to publish a sensitivity number better than you competitor - you can do that by having fine print that doesn't say what the source signal is, what its signal strength is, or what temperature the chipset environment is in during testing, or how its even measured.

Reality is most users of these chipsets have no way to measure the sensitivity themselves as the equipment is specialized and very expensive. GPS signals are 19 dBm BELOW the noise floor, so conventional test equipment wont' detect the signal.

 

[DaveM]

This is not accurate. The iPhone 3Gs uses a GPS chip designed by Global Locate (now owned by Broadcom) and licensed to Infineon, called the Hammerhead II. The sensitivity of the Hammerhead II is rated at -160 dBm.

Most current dedicated GPS devices use the SiRFstar III GPS chip which is rated at -159 dBm. To remain competitive, SiRF/CSR recently announced an updated GPS chip called SiRFstar IV which is rated at -163 dBm for tracking. However GPS devices using SiRF IV have yet to hit the market.

Additionally, the Hammerhead II GPS chip supports A-GPS (assisted GPS) which means it can use cell tower information to reduce the time it takes to acquire a satellite signal and position. Dedicated GPS devices do not have this feature except for WAAS.

Lastly, A-GPS does not need to triangulate with cell towers. The cellular networks already knows the position of each cell tower and it knows which cell tower your phone is connected to, which is the nearest tower, based on signal strength.

Maybe I should have used the word "accurate" instead of "sensitive". It has been reported online, and I have witnessed first hand through friends iPhones, that the iPhone 3g GPS is less accurate than many stand alone GPS units (in particular recreational mapping units). This is especially true when the iPhone can not pick up a cell or wifi signal.

Most stand alone mapping units have WAAS these days.

In order to pin point a location with cell towers you do need to triangulate. Nearest tower by cell strength is used to speed up the sat signal time to first fix (TIFF) location but will not place you on a map by itself.

http://gisandscience.com/2009/07/15...f-assisted-gps-wifi-and-cellular-positioning/

All of that said the iPhone 3g GPS is accurate enough for it's purposes, especially around town. I have been impressed with the iPhone performance in the open spaces of the Sierra Nevada's as well, but I would never rely on it as a mapping or off route unit.

 

[Scott Brady]

I just used Topo Maps on my last two trips. Works perfectly with and without cell coverage. The latest update allows downloading up to 10 full-res quads at a time, which is a big increase in convenience.

For wet conditions, I use the OtterBox case.

 

[Ryanmb21]

Maybe I should have used the word "accurate" instead of "sensitive". It has been reported online, and I have witnessed first hand through friends iPhones, that the iPhone 3g GPS is less accurate than many stand alone GPS units ... iPhone 3g GPS is accurate enough for it's purposes, especially around town. I have been impressed with the iPhone performance in the open spaces of the Sierra Nevada's as well, but I would never rely on it as a mapping or off route unit.

iPhone 3G does not have accurate GPS, iPhone 3Gs does... he's talking about the 3Gs, your talking about the previous generation 3G.

 

[Ryanmb21]

I just used Topo Maps on my last two trips. Works perfectly with and without cell coverage. The latest update allows downloading up to 10 full-res quads at a time, which is a big increase in convenience.

For wet conditions, I use the OtterBox case.

Great tip, I didn't know you can do that. It is described here. I've used this app with our without cell service with good accuracy.

 

[DaveM]

iPhone 3G does not have accurate GPS, iPhone 3Gs does... he's talking about the 3Gs, your talking about the previous generation 3G.

No mention of chip or antenna differences or better accuracy on the Apple iPhone comparison page. From looking around online I see anecdotal reports that the 3g & 3Gs share a GPS chipset. The primary difference between the two is the 3Gs has a faster processor and adds a magnetometer for a real compass. Neither of which increase accuracy.

 

[Ryanmb21]

No mention of chip or antenna differences or better accuracy on the Apple iPhone comparison page. From looking around online I see anecdotal reports that the 3g & 3Gs share a GPS chipset. The primary difference between the two is the 3Gs has a faster processor and adds a magnetometer for a real compass. Neither of which increase accuracy.

Hmm, where did I hear that?..

 

[WickedZJ]

From an ATT employee (my wife) the new 3gs has more memory the magnetometer and a new camera. those are the only differences between the 3g and 3gs.