NetMap's Technical Help Guide

Data Transfer Between NetMap and NHD and Vice-Versa

The NHD and NetMap’s stream layer each can make important contributions to geospatial data archiving, analysis and decision support for natural resource management and in other applications. Some agencies have made large investments in the NHD, but understand the importance of other stream layer functionality, such as in NetMap that can be applied to numerous land management questions, via its suite of analysis tools. In addition, NHD may have key parameters that could be useful with respect to NetMap’s analysis tools. Thus, it is important that the NHD and NetMap stream layers can transfer data between each other.
Transfer of segment scale data between layers can be a challenge. There are differences in the spatial location and alignment of the two stream layers because of the way they were created. There are differences in the headward extent and density of their networks. There are also differences in channel segment length; the NHD may have segment lengths kilometers long, while NetMap’s universal stream layer commonly has segments of between 50 to 100 m. To match segment to segment requires that these differences be accounted for.
A “Cross Talk” tool that would allow data transfer between NetMap’s stream layer and any other layer (including the NHD) is under development with a completion date planned for end of 2013/early 2014.

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