We answer this question quite often. The answer is quite simple: You get what you pay for. The U.S Gulf of Mexico is an excellent example. There are numerous, freely available data sources out there if one if willing to scour the internet, deal with numerous file formats, datums, etc.
Using TCarta Marine’s GIS ready bathymetry data you know that you have the “best available” data in terms of resolution, date, and quality control. With public data you just don’t know what you’ve just downloaded. It could be survey data from the 1990’s when there is data from 2007 available; it could include bad beam values; it could be a noisy dataset. It could be a lot of things. It’s uncertain what you get when you use public domain data.
With TCM data you can rest assured that we have taken care of all the details. You can be certain that you are using the best available data possible. Combine this assurance with the complete data package that TCM provides you that includes high resolution contour lines, a sampling of the depth points, and a high resolution shoreline, you get the complete, best available GIS ready data package at a cost-effective price.