TdhGIS is described as 'Vector Based Spatial Analysis' and is an app in the Photos & Graphics category. There are more than 25 alternatives to TdhGIS for a variety of platforms, including Windows, Online / Web-based, Linux, Mac and Android. The best alternative is QGIS, which is both free and Open Source. Other great apps like TdhGIS are OpenLayers (Free, Open Source), PostGIS (Free, Open Source), GRASS GIS (Free, Open Source) and ArcGIS (Paid).
QGIS, formerly Quantum GIS, is a user friendly open source Geographic Information System (GIS) licensed under the GNU General Public License that runs on Linux, Unix, Mac OSX, and Windows and supports numerous vector, raster, and database formats and functionalities.
OpenLayers is a high-performance, feature-packed library for all your mapping needs. FEATURES Tiled Layers Pull tiles from OSM, Bing, MapBox, Stamen, MapQuest, and any other XYZ source you can find. OGC mapping services and untiled layers also supported.
GRASS GIS (Geographic Resources Analysis Support System) is an open source, free software (FOSS) Geographical Information System (GIS) with raster, topological, vector, image processing, and visualization functionality.
ArcGIS is geographic information system (GIS) software for visualizing, managing, creating, and analyzing geographic data. Using ArcGIS, you can understand the geographic context of your data, allowing you to see relationships and identify patterns in new ways.
MapWindow is a fully free and open source geographic information system project. It includes an open source programming component, MapWinGIS ActiveX, and an extensible desktop application that supports plug-ins written in .NET (C# and VB.NET).
gvSIG is a Geographic Information System (GIS), that is, a desktop application designed for capturing, storing, handling, analyzing and deploying any kind of referenced geographic information in order to solve complex management and planning problems.