Gmap4 = View topos/aerials *offline* and your geolocation

I have posted here before about Gmap4 which is an enhanced Google map viewer that I developed. Up until this summer I believed that Gmap4 would not work if your mobile browser was offline.

I was wrong.

If you follow a few simple instructions, many (but not all) of the Gmap4 features will work just fine on a smartphone, tablet or other mobile device when you are offline. Among other things, when you are offline you can:
* Look at high resolution topo maps (t4 Topo High)
* Look at Google aerials
* Look at other basemaps
* Look at GIS overlays
* Turn on the geolocation feature (Menu ==> My location) and see the map become centered where you are standing
* Move and watch the location symbol follow you and the map automatically move as needed
* Touch the location symbol and see your coordinates in the current coordinate format
* Change the coordinate format
* Turn on/off a UTM grid
* Turn on/off a USNG grid

Yes, you can do all of the above while the browser in your smartphone or tablet is offline. Now let’s pop the hood and see how this works.

Any map you see with Gmap4 consists of a bunch of small image files called “tiles” that are stitched together to cover your screen. When you look at a map while you are online, a copy of each image file is saved in the browser’s cache. If you keep the browser tab open that has the Gmap4 map, then you can then go offline and still pan the map over the area for which there are map tiles in the browser’s cache. If you pan too far, the screen will be white.

To read plain English instructions that I guarantee you will understand (I don’t know how to write computer babble-speak) please visit the Gmap4 Help page and download the pdf file “How To Use Gmap4 Offline”.
Help page: http://www.mappingsupport.com/p/gmap4_help.html

From the Help page you can also find the FAQ, examples, a Quick Start guide (also on the Help page) and more.

Gmap4 default map: http://www.mappingsupport.com/p/gmap4.php

Joseph, the Gmap4 guy

Great! thank you for developing Gmap4, it is by far my favorite map website. I love the functionality of it, and I have been slowly converting my other hunting buddies.

I have been using it exclusively for the past two years as well. Thank you

I'm a little leary that it uses the browser's cache. Seems a little risky. Apps like Atlogis create their own file directory and save maps there. Or, am I missing something?

Enable unlimited downloading to my drive, ability to create tiled jpg and compile to KMZ for a Garmin, ability to add georeferenced tiff/sid/etc, ability to add .shp and I'll be a paying customer. Then develop an Android/IOS app and add the ability to write and transfer those maps/markups from the desktop version to the handheld and you'd really have something. Essentially a better version of TopoFusion.

Dang! There is a God!

JDZ said:

I'm a little leary that it uses the browser's cache. Seems a little risky. Apps like Atlogis create their own file directory and save maps there. Or, am I missing something?

Click to expand...

There are 2 kinds of apps: Native apps and Browser apps. Gmap4 is a browser app.

A native app can access the file system on the mobile device as you describe. But, if you write a native app, you need to do it twice. Once for Apple devices and once for Android. Then you need to maintain both sets of code. The only way for a user to get a native app is by downloading it from an app store and installing it.

By contrast, if you write a browser app you only do it once. The app happily runs in almost any browser on almost any device. However, browser apps do not have access to the file system on the device. Browser apps do not have to be downloaded or installed. You start a browser app by clicking/touching a link.

Bottomline: No one tool is perfect for everybody in every situation. The ability to use Gmap4 offline is simply another tool you can have in your toolbox.

Joseph