2

I am trying to figure out how to get notified when a map layer is updated on this county government map server.

I am not a developer, so I am in way over my head, but I figured out the various map layers here. I want to know when layer 14 is updated but can't figure out how to do that without downloading the whole map and using a md5 checksum to see if it changed.

Is there a command I can send the API that will tell me when the layer has last been updated?

Ideally, I would like to create a script that checks every 30 minutes or so and can notify/email me when it has changed.

  • 2
    There is no cyber-stalking sub-component to the REST API. In fact, there's no guarantee that the service would change in any way if the data was modified in a enterprise or file geodatabase. Your best chance is to ask the publisher to advertise changes, either by a social media feed or by adding a trivial servlet to the web server. That would be very much out of scope for GIS SE. – Vince Sep 27 '17 at 3:16
  • I vote that this question should remain open - it's a reasonable question – Stephen Lead Sep 27 '17 at 4:05
  • I agree that it should remain open. @Vince - please consider adding your comment as an answer. While the solution you suggest is out of scope of GIS, there may be others who have experience with this issue and have other ideas. Also, your answer is valid so it may help others with this question (who are likely GIS professionals). – jbalk Sep 27 '17 at 4:24
1

As @vince says, the best option is to speak to the owners of the website and ask if they can set up an official channel to communicate this.

While there is nothing available on that layer to show when a change has been made, technically it will be possible to write a program to access the data programmatically and detect the changes yourself.

The legality of this is another matter. You could argue that you're merely accessing the same data which is visually available on the map, but in an automated format.

You can obtain the raw records of the Areas Scheduled for Spraying layer using a query to this URL:

http://gbawebpro.vcgov.org/PW/Proxy.ashx?http://vgis3/ArcGIS/rest/SERVICES/PWPublicSvcs/MapServer/14/query/?where=1%3D1&f=json&outFields=DateTreated,MethodTreated,Status,WorkOrder

This requests all records (where 1=1) in JSON format (f=json) for the fields specified in the outFields parameter.

This won't tell you whether something has changed, but you could run this query in a script every 30 mins and compare the latest result with the previous result, and calculate the change manually (eg by examining the date, locname, work order and status fields).

Actually detecting the changes, and emailing you when they're found, is outside the scope of GIS Stack Exchange. But a competent programmer using something like Python could put this together reasonably easily.

|improve this answer|||||

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.