Scanned topographic maps, sometimes known as Digital Raster Graphics (DRGs), offer unparalleled mapping information such as infrastructure, land use/land cover, terrain and rich place name data. This information is not usually available in aerial photography or satellite imagery products. Unfortunately, the creation of topographic maps (typically by large government map agencies) is a very expensive and time-consuming process. This means that even by the time they are printed, some aspects are already out of date. Essentially, no topographic map will ever be of recent vintage in the same way as aerial photography or satellite imagery, but again, it can offer information that won’t be found in other mapping products.
The level of detail and accuracy of a map is related to its scale. Below are general guidelines for horizontal accuracy at 90% confidence (meaning that 10% of features would not meet these specifications); however, actual results will vary based on publisher, vintage, production methods, terrain type and other factors:
- 1:10,000 ~8.5 meter CE90 (Circular Error 90%) horizontal accuracy, typically suitable for activities on foot, such as hiking
- 1:25,000 ~ 12.7 meter CE90 horizontal accuracy, typically suitable for activities on foot, such as hiking
- 1:50,000 ~25.4 meter CE90 horizontal accuracy, typically suitable for off-road vehicle activities
- 1:100,000 ~50.8 meter CE90 horizontal accuracy, typically suitable for some off-road vehicle activities
- 1:200,000 ~101.6 meter CE90 horizontal accuracy, typically suitable for aviation and limited off-road vehicle activities
- 1:250,000 ~127 meter CE90 horizontal accuracy, typically suitable for aviation and limited off-road vehicle activities
- 1:500,000 ~254 meter CE90 horizontal accuracy, typically suitable for aviation activities
Typical vertical accuracies are one-half the contour interval. For example, a typical 1:50,000 scale topographic map has a 20 meter contour interval (i.e., it shows a contour line for every 20-meter change in elevation) Therefore, the vertical accuracy would be ~ 10 meters.
Some map datasets won’t mosaic/match well across adjacent sheets, especially if the maps were made at different times, using different methods.
Many parts of the world aren’t well mapped, so the ideal mapping (e.g., desired scale, vintage) may not exist. In that case, one must decide whether it is still advantageous to obtain the best available mapping. Please understand that LAND INFO did not create the maps, and is not responsible for their content. LAND INFO provides the service of assembling the maps (often from diverse sources globally) and converting them from paper to digital format (although in some cases, the maps are sourced in digital format). The accuracy and completeness of the data is beyond the control of LAND INFO and is explicitly not guaranteed. Data not to be used for navigation.