Do your homework when considering After Market programs.
~ Captain Paul's response to: ~ BUDP ~
I have seen the software at a variety of launches in the southeast Louisiana area, but I have not actually used the product.
When ever considering any after market product, there are several things that you may want to consider. To determine if is will actually work in your GPS unit.
First, is the product only aerial photos pieced together as supplied by the NASA High Altitude Photo service or are they Ortho Corrected photos? Ortho photos have been corrected to take into consideration the curvature of the earth at the latitude~longitude where the photo was taken. Ortho photo maps may be as much as 300 feet off from an uncorrected photo image of the same specific site. The product should state the date that the images were obtained or when the map was complied. Were the images taken within a reasonable time frame or were they taken fifteen to 25 years ago?
Second what is the scale of the map, and does it match the scale of the internal settings of your GPS unit. Are distances set in feet, meters, nautical miles, etc.
Third, what DATUM was used to capture and plot the images. This is similar to but not exactly the same correction as an ortho photo image. A difference between NAD 27, NAD 83 and WGS 84 could mean as much as 280 feet difference in a position. Again this may not make a difference if you are trying to find a seven story oil~gas platform or a singular prominent point of land, but if you are looking for an opening to a small bayou, an artificial underwater reef of your uncle Sam’s honey hole, the difference is very important.
Fourth, if it states positions, are they in Decimal degrees, Degrees, Minutes and Seconds, Degrees, Minutes and thousandths of minutes? Does this data match the position format that in being used in your GPS unit.
And, does it credit the source of the data that was used to compile the actual mapping. No commercial company that I know of has the ability to actually “make” a map by themselves. Cost necessitates that they use official government sources as a basis of their program.
Mapping programs should clearly list all of these attributes in order to allow modern GPS units that are capable of discerning a position to within 3 meters to get the most out of the mapping program when inter-phased with a GPS unit.
You can compare the map, by going to several very specific points in the area of coverage, and captured a waypoint point. Then change the mapping software to the mapping software that came in your Lowrance HDS unit. How does the Lowrance mapping software depict your position at the same location and if not what is the position stated on that software.
If you were to find that the map positions did not totally agree with the factory program, any position you may give to a buddy or get from a buddy of a published source will not agree to where the position is actually located.
It is up to you to determine if this or any other program meets your requirements. The price is certainly right.