Add more flexibility than 2 points when georeferencing map sheets?
I love CalTopo's georeferencing capability. And if the map you've imported to create a georeferenced map sheet is an accurate one, the 2-point method seems to work fine.
However, sometimes maps are just...off. And even when carefully choosing the best 2 points, it just won't align well with an accurate basemap.
What would be really helpful in these situations is to add functionality like Google Earth, where you can "stretch" a map sheet via side handles to "force" it to align with the basemap. (In other words, stretch the map sheet without maintaining the original proportions of the map sheet.) Often all it would take to align a map perfectly is just tweaking only the width or the height of a map sheet (independent of one another).
In Google Earth, this is easily done by using midpoint handles on all 4 sides (grabbing a midpoint handle will only adjust the map sheet in that direction). If you want to proportionally adjust the entire map (e.g. scale it proportionally) you just use a corner handle.
Just a suggestion—thanks!
Scott in Oregon
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Good points (no pun intended, I think). I would even settle for the ability to register a third point as part of the process. I will say, though, that often persistence pays off and I'm eventually able to get a "near perfect" georeferencing by alternately re-registering the first and second points in slightly different locations. There is also a bit of an art to negotiating the buggy interface, as you may have found, where the map sheet pings wildly across the base map as you scroll (so distracting!), and where it's easy not to notice through all this noise that the right-click dialog box has errantly moved to fit the screen and in the process moved your targeted coordinates out of position before you add them.
I get it. It's not easy implementing bespoke GUI functions that work well the first time, so I just hope Caltopo development team's ongoing ghosting of the help forum here is a sign they're studiously taking notes and hard at work.
Agreed Brett! I’ve also tried resetting the 2 points to different places to get better alignment, and sometimes that helps.
Also agreed on your perfectly described pinging of the map sheet across the basemap, LOL Like you, I can tolerate that (I’ve even learned to predict the pinging and work with it).
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