Frequently Asked Questions

Is there an API?

No, Equal-Area-Maps.com does not have a programming interface (API). It is intended as a demonstration of online equal area maps. The components are all open source components (primarily UMN MapServer and OpenLayers), so you are free to implement your own online equal area map(s). See the How To page for more information and links to the GeoWeb Guru articles that describe how these maps work.

Winwaed Software Technology LLC (owners of both the Equal-Area-Maps.com and GeoWeb Guru websites) can be contracted to create similar online map applications, if necessary.

Why is the map not updated with any data from the GeoRSS/KML overlay that I specify?

There are a number of possible reasons for this. First, the file must be a valid KML file for the KML option. KMZ files are NOT supported. GeoRSS files must also be valid. At present, only point markers (pushpins) are supported for GeoRSS files.

Both GeoRSS and KML files are limited to 5MB. The larger a file is, the longer it will take to load. A 5MB file might take a minute or so - even if you have a high bandwidth connection.

There are also a number of settings which are intended to restrict abuse. Unfortunately these might also impinge on normal use. Map session identifiers are very short: an overlay must be applied within about 30 minutes of the original map page being loaded. Your browser must send requests with valid referrer fields. Finally there is a flood limit to limit activity at busy times. Try again later, and refresh the map page just before you enter the GeoRSS/KML URL.

Why are there no overlay options for many of the projections?

The overlays are implemented with OpenLayers which uses the Proj4JS library to reproject GeoRSS and KML data. Not all of our projections are implemented by Proj4JS, hence we cannot provide the overlay feature for all projections.

Proj4JS is an open source project, so you would be welcome to add support for new projections if you need them. This is what we did for the "Cylindrical Equal Area" (Behrmann) projection.

Can you provide more detail on the basemaps for higher zoom levels?

The maps are intended for use as global maps. These are maps which should be viewed at a global level, or only zoomed in slightly. As such, more detail would not be visible. Greater detail will also result in slow map delivery and use valuable bandwidth.

If you wish to view maps that are zoomed in with more detail, then you probably do not need to use a global equal area projection. Even the need for an equal area projection is diminished at high zoom levels. One of the commercial online map services (eg. Bing Maps, Google Maps, or MapQuest) should be used instead.

The polar maps are not global and do not appear to be equal area projections?

This is correct. This site was originally created for a series of articles at GeoWebGuru. Due to the success of these articles and maps, we received requests for polar map projections. The working examples are supplied on this site alongside their predecessors (the equal area maps), although only one of these polar projections (the Lambert Azimuthal Equal Area) actually has the equal area property.