[Therion] trouble with joining scraps while digitizing an old map

[Stacho Mudrak]

As MartinS wrote, you will definitely need some reference points, but they do
not need to be stations. In the case, if there are no survey data - all you
need to do is just to scale each scrap properly.

I would do following steps:

1. Put some grid on the scanned images according to scale. Ideal is some real
coordinate grid like UTM, but also some local coordinate system is OK.

2. Then set X Y coordinates of two real points and two points on the JPG image
for each scrap in the section - you have to set them in "Scraps" tab in map
editor - under "picture scale points" and "real scale points".

In fact you have to calibrate the scraps same way, as you do it for
cross-sections (with exception, that projection is plan). See Wiki for
details:

http://therion.speleo.sk/wiki/doku.php?id=tbe:wiki3#cross_sections

After calibration - each scrap should be displayed on the correct place and in
the correct scale. If you will enter real coordinates in some, UTM grid - you
have to add "-cs UTM32" option to the scrap, that it will know where to put the
scrap.

HTH, S.

Quoting Jonathan Prouty <dormat at gmail.com>:

> I decided to digitize an old map of one of my favorite caves. The JPG of the
> entire original map was too big for therion to load, so I cut it up into
> smaller images that will load.Tracing the map and compiling it worked
> perfectly for the first section that I digitized (section_1.th2). I moved
> onto the second one, traced the old map same as before (section_2.th2). All
> that is pretty straightforward.
> 
> The problem arises when I try to join scraps from section 2 with scraps from
> section 1. The join fails miserably. I tried to follow the instructions from
> the wiki
> (http://therion.speleo.sk/wiki/doku.php?id=tbe:wiki4#importing_maps),
> but it seems the instructions are geared towards joining unsurveyed data
> with surveyed data. I don't see how to join unsurveyed scraps with other
> unsurveyed scraps. I have no "fake" data like the instructions suggest.
> 
> I've included links to an image of a portion of the old map I'm digitizing
> and to a PDF that therion spit out. Comparing the two will make the problem
> very apparent. I'm sure there is a pretty straightforward solution, I simply
> don't know it. Thanks in advance in for the help!
> 
> http://www.talkingnerdy.com/jonny/images/slices.png
> http://www.talkingnerdy.com/jonny/images/byers.pdf
> 
> -Jonny
> 
> P.S.
> Just in case it wasn't clear, I don't have access to any of the original
> survey data. The cave was surveyed in the 60s. I'd be surprised if the
> original data still exists.
> 
> 
> -- 
>       ^v^
>  ^v^   ^v^      Take nothing but pictures,
>     ^v^       Leave nothing but footprints,
>  ^v^       Kill nothing but time.
> (**)
>