TransDEM Forum

Fantastic program. I do have a "wish-list" item. I get "follow-up" errors when adding map tiles from Google Maps (just as others have reported in this thread). It occurs after getting a certain number of tiles. That's when Google decides to send a captcha (which we can't see or handle, since Transdem is not a web browser). Unless you correctly solve the captcha, you are blocked for a long period of time. So here's the wish list item. It would be nice if there was an optional way to do an interactive, semi-automated download of each tile on the route. This would be similar to the way Transdem follows a route and gets tiles today, but after each tile on the route is downloaded, a mini-browser window appears where you can see the tile (or captcha screen) and click a button (or solve the captcha) to continue. Obviously this one-tile-at-a-time approach would be slower and more tedious, but it would be optional, and I think it deals with the issue in a way that doesn't violate Google Maps terms of service.

Map Tiles are some sort of de-facto industry standard. There are a few details where the providers have implemented it differently, in particular the tile address scheme, and one is using an ellipsoid instead of a sphere, but they all can be accessed in plain session-less http mode. Some may limit the number of tiles in this mode. I have not analysed the existence of session-oriented modes and how those might be implemented. They would not be part of the standard anyway.

You could try to "cheat" here. If a TransDEM path aborts prematurely you could shorten this path, reconnect your internet connection, hereby obtaining a new (dynamic) IP address and start over.

Thanks. I tried getting a new IP address, but if I disconnect my cable modem and reconnect, my Internet Service Provider assigns me the same IP address every time. It's supposed to be dynamic, but that's the way it works. They probably assign a new IP address only if the cable modem is disconnected for a few hours. Not a big deal. I was eventually able to get all the Google Map tiles I need, over the course of a couple days.

Glad to see some discussion on this as it is probably the only really frustrating thing using Transdem and obviously, as noted in the previous posts, largely due to external factors.

If I could just pass on one nugget of knowledge, it does seem to increase the chances of getting all the maps in one hit if you avoid doing anything else while Transdem is running the process. Even just tabbing to an IE window and doing some browsing seems to affect the outcome. Obviously this is a very memory intensive process both at the Transdem end and the server end.