Messages posted here can also be received as emails: information pre-print options:     

Templot Club Home list recently active topics
  Search  Image Gallery  My Account  Members  Help       


 
Forums and resources for users of Templot track design software about Templot Club

Please click: important information for new members and first-time visitors.
 
quick links: files, photos and messages archive on Yahoo
A single message from topic:  Ludgate Hill North   in forum:  Share and show
main Templot web site

Single message by Martin Wynne       Topic: Ludgate Hill North
Posted: 26 Sep 2017 12:51
 PM  Reply with quote  Reply blank  Go to topic 
Martin Wynne
West Of The Severn, United Kingdom



view images in gallery
view images as slides
Hi Howard,

Here I have overlaid the 1951 version (transparent) over the 1890s version (white area):



Notice a couple of things.

1. Templot has got them both to the same scale for 4mm/ft. Which may not seem much of an achievement on the face of it, but in fact I'm very pleased that it has worked ok. :)

The 1890s map has been resampled and georeferenced by the NLS for their "slippy" map on the web site, and the scaling maths is based on the latitude and zoom level using the known circumference of the Earth at the Equator.

The 1951 "Find by place" map has not been georeferenced, it is displayed by the NLS exactly as scanned from the original sheet based on the OS National Grid, which uses a different map projection. I spent a long time looking at different maps on the NLS web site to establish scaling factors for use in Templot.

2. Because of the different map projection, in order to get a match it was necessary to twist the 1951 map. The angle varies according to the location. There are tools on the OS web site to perform such conversions, but in practice trial and error is probably just as good for the old maps. I found that this one needed a twist of -1.7 degrees.

In most cases Templot users will be using one or the other, not both, so this angular difference is of no significance. The finished track plan is likely to need shifting and rotating anyway for convenient printing and to match the railway room.

p.s. The transparent option is useful for aligning different screenshots and maps, but it prevents deep zooming when aligning tracks over them, and makes zooming and panning significantly slower. So having got it in the right place, it is better to switch off the transparency for actual use. Just how much difference it makes depends on the graphics capabilities of the system. 

regards,

Martin.


A single message from topic:  Ludgate Hill North   in forum:  Share and show
about Templot Club

list recently active topics Templot Companion live online chat Please click: important information for new members and first-time visitors.

Please read this important note about copyright: Unless stated otherwise, all the files submitted to this web site are copyright and the property of the respective contributor. You are welcome to use them for your own personal non-commercial purposes. If you want to re-publish any of this material or use it commercially, you must first obtain the owner's permission to do so.

The small print: All material submitted to this web site is the responsibility of the respective contributor. By submitting material to this web site you acknowledge that you accept full responsibility for the material submitted. The owner of this web site is not responsible for any content displayed here other than his own contributions. The owner of this web site may edit, modify or remove any content at any time without giving notice or reason.
Problems with this web site? Contact webmaster@templot.com.
Powered by UltraBB - © 2009 Data 1 Systems