Hi,
I noticed in your demo that the map does not wrap; that is to say when you reach the west edge of North America and you attempt to continue panning towards Asia the map does not pan any further. Is this a restriction of the shapefiles used to create the World Map Kit or a limitation of the control?
Steve,
This is currently a limitation of the coordinate system and the control. Each point on the earth in decimal degrees and various projections need to have a coordinate system that defines where they are. When we go to display that on a drawing surface it is difficult to keep that system cohesive if we supported the wrap around panning. I do not think it would be impossible but add allot of extra complexity. This is why you never see this on other mapping components or GIS tools. Where you do see it however are things like Google Maps and other image tile based system. The reason is that it is easier for them because they do not offer any read GIS functions other than lining up images. You cannot track zoom in, draw a line between two points, or draw track shapes between the two systems… They also have only one projection format and do not have to support others.
Having said all of that I think this is something we can consider and I am going to add a note to this issue I our tracking system. The short answer is at the moment we do not have it. If there was a big project that had to have this and it was a show stopper we might be able to get something to work.
David
Hi David,
It is possible using ESRI by re-defining the Central Meridian in the ProjectedCoordinateSystem. To pan west you take the old CentralMerdian subtract say 20 degrees, apply the new value, refresh the control and repeat the process as you move further West. One of the guys I know at ESRI sent me a working example.
Regards
John
John,
Thanks for the tip. We will play around with this today. Could you sent the code you go, I am interested to see what they did as a zip attachment?. If not no problem I pretty much understand what you are talking about. One thing to note is that in my understanding once you take something like decimal degrees and you project it to do this kind of thing then the map is no longer in decimal degrees and will measure in feet or meters. You can always de-project back to decimal degrees though.
David
Hi David,
I'd need to check with the guys at ESRI before releasing any code. As you said this is basically very simple.
It's a projected coordinate system based on WGS84WebMercator, the pan left and right buttons basically do as I said, add or subtract 20 from the CentralMeridian in the ProjectedCoordinateSystem and then refresh the map control. There is nothing special so far as the map goes it'sjust a plain ol' SHP of the World initially based around the Greenwich meridian.
I need to check into the Degrees/Map Meters issue, I'll do some poking around...
Hope this helps
John
John,
Which product of ours are you using, Desktop, Web or Services? I am curious as the solution might be a little different depending on how you want it to work. For example in the desktop and web we already have a panning features that moves the view port. We would have to make some changes to make this new functionality happen. Another approach would be to add a set of pan buttons that move the map and the pan still moves the view port. I think it is easy enough to change the projection but we need to know how you want the rest of the functions to work. Another thing that would need to happen is that the projection would need to be updated on all the layers to keep them all in sync as well. Now allot of work but something to keep it all working properly. You would need to keep all your user defined points in something like decimal degrees. I say thins because since you are changing projections all the time, moving the meridian, it will effect the coordinates and we will need to keep that straight. Any insight into how you would want this to work would be valuable.
David
Hi David,
We are using the Desktop for the moment but eventually both.
Currently we work exclusivley with a WGS84 Mercator projection as that is what mariners are most familiar with. I agree that the only sensible units would be good old latitude and longitude, at least that is constant whatever the central meridian for the projection is. Apart from that I'm quite relaxed about this if you can get it going, we will alter our stuff to suite, said he dodging the question
As a starter it would be nice to see what has to be done in order to get Countrieso2 to 'scroll'
Regards
John
John,
This week went by so quickly. I promise to work up a demo next week, hopefully early next week to show this. I think this is possible and would be a really cool feature. I am not sure if we can get it seamlessly integrated however we should be able to get some sort of way to wedge this in there. The Desktop and Web editions are very different and I think we will focus on the Desktop first as we have more control over it in a number of ways. If you could please reply to this so it stays in my work queue as a reminder to have this scheduled for Monday.
David
Hi David,
A reply as requested!
Looking forward to seeing the demo.
I posted one in the Desktop forum this morning about a roamap for the release of Desktop 3.0, did you see that?
Regards
John
Hi David,
This one seems to have gone a little dead, are you still working on the this?
Regards
John
John,
It’s not dead yet, actually it’s feeling a little better. We have not had time to schedule it due to a bunch of other items in the queue. It will be looked at though I assure you. I just need a person to give it to and be able to have him focus on it until completion. Thank you in advance for your patience on this. Please reply to this to keep it in my queue. :-)
David
John,
I saw this get tasked out this week, we have not forgotten about it. You will see that very soon there will be some new posts in the developer blog on a bunch of new formats and stuff. It has been a very busy time for us so sorry for the wait.
David
I let you that I have been tasked to create a blog on that topic. I will thoroughly explain how to implement that effect of seeing the Pacific Rim when panning to the West. I will also add a sample app to the blog. That should be completed by the end of this week.
Please see the blog at
gis.thinkgeo.com/Support/DiscussionForums/tabid/143/aff/16/aft/5613/afv/topic/Default.aspx