Using locally saved Data Sources

Jeff254

Can I define a locally saved Data Source for use instead of the Default Sources defined in Global Mapper. For instance I have downloaded SRTM 1arc Datasets from USGS in .dt2 format. But am not sure how to create my Source such that I can pull the Data from this local Source instead of from the Predefined source in Global Mapper

Mykle

Jeff,

Simply save your downloaded data to a local file, taking care to limit the resolution and data extents to your project area. 

Note that the default resolution is the maximum available from that source.  For SRTM the maximum is reasonable, but for other sources like imagery it is much more detailed.  Likewise the default extents may be worldwide.  Attempts to save more than you need will require more time, and may not succeed.  

Some on-line sources, like maps, may require a few iterations as you determine an acceptable value for the resolution.  Start with large values (more meters per pixel) and repeat with smaller values until you have a file that is usable for your project. 

Also note that some on-line sources are protected and cannot be locally saved. 

Finally, also note that servers are not guaranteed to be on-line, the address may change, or the data may change.  None of these are good for a project that is not completed immediately. 

When your data have been saved, close the on-line source and load your saved file(s). 

Finally, note that saving data locally is much more efficient.  Global Mapper will re-download on-line data as you work with your project, slowing (interrupting) your workflow a lot. 

The extent of your local data files will be limited, so you will need to repeat the exercise when you create new projects in different areas.  I regularly do this when I start a new project, and when the project is completed, all (or most of) the data can be archived. 

Jeff254

Mykle said:

Jeff,

Simply save your downloaded data to a local file, taking care to limit the resolution and data extents to your project area. 

Note that the default resolution is the maximum available from that source.  For SRTM the maximum is reasonable, but for other sources like imagery it is much more detailed.  Likewise the default extents may be worldwide.  Attempts to save more than you need will require more time, and may not succeed.  

Some on-line sources, like maps, may require a few iterations as you determine an acceptable value for the resolution.  Start with large values (more meters per pixel) and repeat with smaller values until you have a file that is usable for your project. 

Also note that some on-line sources are protected and cannot be locally saved. 

Finally, also note that servers are not guaranteed to be on-line, the address may change, or the data may change.  None of these are good for a project that is not completed immediately. 

When your data have been saved, close the on-line source and load your saved file(s). 

Finally, note that saving data locally is much more efficient.  Global Mapper will re-download on-line data as you work with your project, slowing (interrupting) your workflow a lot. 

The extent of your local data files will be limited, so you will need to repeat the exercise when you create new projects in different areas.  I regularly do this when I start a new project, and when the project is completed, all (or most of) the data can be archived. 

You are correct on most of the points here. Actually the reason I want to have the data sets locally is to imporve on the speeds when working with the files. And as you said "...... servers are not guaranteed to be on-line, the address may change, or the data may change.  None of these are good for a project that is not completed immediately...." 

Now my issue is this. I already have downloaded the data from a Public Source. Now I want instead of using the Default online data option which takes me to the same public source, I want to be able to refer to my local source. Currently am simply opening the Data Sets as a layer one by one. But I hope with time I can combine all these datasets into one file, and then the user can always load the Data set to suit, just like the truly online sources. For your information I download Data Sets for the entire country, and we normally deal in projects from all over

In Summary:
     1. How do I create a local Data source using .dt2 files ( Data from USGS)
     2. Best way to combine several .dt2 files into one file for use as a source