Using Geospike Without Data
Don't have internet? No worries! Geospike works without data, you can create new spikes and edit recently created ones completely with no data. When you next use the app with data, it will sync everything up.
Geospike should be able to get your location without an active data connection, but there are a number of differences. The GPS hardware in your device can take longer to find your location when you don't have an active data connection, and longer still if you also don't have any cellular reception (e.g. no SIM card is installed). Once you get one fix, subsequent ones are often much faster. If you travel a great distance (e.g. to a new country), then the first fix may take up to 10 minutes, and you may need to have a clear view of the sky.
NB. when Airplane mode is ON, iOS cannot get your location. If you wish to test a "no data" environment, or simply use your iOS device without a SIM card, you can either remove the SIM card, or add a PIN code to it and don't enter the PIN when prompted (it will say "SIM Locked", preventing phone calls but enabling the GPS to work).
Always have Wifi Enabled
Both iOS and Android use the Wifi hardware to improve the location fix. This is especially important while inside buildings and in cities with tall buildings (think New York). Even if you don't have wifi connected, you should still have it enabled to take advantage of this.
Later models of the iPhone (4S and later) are particularly good at finding your location without data, as they include the Russian GLONASS system (basically, the Russian version of GPS) for even more satellite coverage (especially in Russia!). This also improving the accuracy of spiking with data.
iPad's marked "Wifi + Cellular" have real GPS hardware, while ones just marked "Wifi" do not. Thus, the Wifi + Cellular models will be far superior if you spike without data.
In our experimentation, Android devices are not as good at getting your position without a data connection compared to iPhone. As a rule of thumb, the more expensive the Android device, the better it probably is at finding satellites. If you plan to do a lot of spiking without data, then a higher end model is recommended (make sure you test it before your trip by pulling out the SIM card, and disconnecting Wifi).
If you need more advanced offline features such as viewing & searching your entire history of spikes, then consider the GPS Log app. GPS Log works perfectly with Geospike and adds many offline features such as full history searching & editing. Visit GPS Log's No Data page for more information about spiking without data on GPS Log.