Many iOS devices have a built in GPS receiver, and will work very well with iSailGPS even if you do not have a cellular data plan. The confusion comes about because the GPS receiver and the cellular radios are both included in the same package. If one buys an iOS device without the cellular radios, then he doesn't get the GPS receiver either. But the GPS receiver and the cellular radios can work independently. When the GPS receiver is first turned on by an App requesting to use it, if you have a cellular plan and a network connection, the GPS receiver will use information that it gets over the network connection to more quickly lock onto the GPS satellites. But if there is no cellular plan, the GPS receiver will get that necessary information directly from the GPS satellites, which can take a minute or two (just a like a separate GPS unit would). Once the GPS receiver is locked onto the satellites, it does not use the cellular plan at all, and its performance is identical whether you have a cellular plan or not.

Yes, iSailGPS is a native iPad App, with full support for the Retina display in the newer iPads. Apple installs a GPS chip in the WiFi+Cellular versions of the iPad. Thus, all features of iSailGPS work with these iPads. The WiFi-only versions do NOT have a GPS chip, but chart download and viewing is still supported by iSailGPS. To access all functions of our software with a WiFi-only iPad, add an iOS-compatible external GPS receiver.

Yes, iSailGPS works on the iPod touch. The iPod touch does NOT have a GPS chip, but chart download and viewing is still supported by iSailGPS. To access all functions of our software with an iPod touch, add an iOS-compatible external GPS receiver.

Yes. There are some iOS-compatible external GPS receivers available. These can offer improved GPS performance over the built-in GPS chip, or full functioning for those Wi-Fi only devices which do not have an internal GPS chip.

To view a chart for somewhere other than your current location, follow these steps:

1. Tap the Chart List tab.
2. Tap the + button. Choose one of the methods to identify the desired chart. Download it.
3. Scroll to this chart in the list.
4. Tap the chart name.
5. A check mark will appear next to the name indicating that is the chart you will view.
6. Tap the My Location tab once only. Do not tap it a second time.
7. You will be viewing your chosen chart, starting in the center of the chart. Pan and zoom to the area on the chart that you want to see.
8. To resume viewing your current location, Tap the My Location tab with the chart showing.

Almost all modern mapping programs accept GPS data in the GPX file format. Use iSailGPS to email tracks, routes and waypoints to yourself or friends. The email has an attachment which can be imported into any application which will read GPX files. Or you can transfer the GPX waypoints, routes and tracks to your computer using iTunes File Sharing.

Send an email to your iPhone, iPad, or iPod touch with a GPX or LOC (Geocaching) file as an attachment. Use Mail to view the email. Press and hold the attachment icon to send the data in the GPX file to iSailGPS.

You can also transfer the waypoints, routes, and tracks from your computer using iTunes File Sharing or Dropbox.

You can change several settings to reduce the devices's drain on its battery. Adjust the following settings:

• Tap Wi-Fi, then Turn off Wi-Fi.
• Tap Bluetooth, then turn Bluetooth off.
• Tap Display & Brightness, then turn down the screen brightness to the lowest acceptable level.
• Tap “iCloud”, then tap “Documents & Data”, turn off “Use Cellular”.
• Tap “Mail, Contacts, Calendars”. Tap “Fetch New Data”. Turn off “Push” and tap “Manually” under Fetch.
• Tap “iTunes & App Store”, then turn off “Use Cellular Data”.

Also:

• Plug the iOS device into a charger before your trip so that you start with a completely charged battery.
• On the Track Screen, select “Always”. Put the iOS device to sleep when you are not looking at it. When you drop anchor or dock, on the Track Screen select “Off”. (Don’t forget to turn tracking back on before resuming your trip.)

If you follow all the steps, you may be able to record tracks for about 10 hours of actual sailing. Use an external battery pack to extend this time.

NOAA charts are huge images (up to 115 megapixels, 55 x an HDTV picture), which take a second to process given the speed of the iOS device's processor. A spinning activity indicator will show in the upper right corner of the screen when the chart cache is updating. Wait to give iSailGPS further commands until the activity indicator is no longer visible.

Originally iSailGPS stored downloaded charts in the documents folder on your iOS device. That way they were backed up to your home computer everytime you did a system backup. With the introduction of iCloud, Apple required us to move the charts to the cache folder. That way the charts, which use several megabytes of memory each, would not take up space in your limited iCloud storage allotment. However with the introduction of iOS 5, Apple started purging files from the cache folder whenever the the iOS device's storage memory was too full. If your charts disappeared, that means that you are almost out of storage memory and would benefit from removing some old apps you never use, some old songs you never listen to anymore, etc., to free up some memory and prevent further problems.

If your charts have been erased, each time you start iSailGPS you will be given an opportunity to re-download your previously-downloaded maps. Be sure to do so before you download any new maps.