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I am using ESRI based GIS software, Postgresql/PostGIS/ArcSDE DB and we have a Mincom Ellipse asset management system.

Currently our all our spatial information regarding asset sites have been recorded as points, this has been versatile for the fact that it accommodates mapping at various scales. Now that we are integrating our Asset Management System with our GIS database the asset management guys want the GIS features to reflect the structure e.g A building footprint as a polygon instead of a point.

My question in terms of the spatial data management. Should I be maintaining two sets of data? One for the asset representations and then one for various mapping tasks?

Thanks DB

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Which asset management system? – Jay Cummins Dec 1 '10 at 11:00
If this is specific to Minicom Ellipse, you should edit the question to make it more clear. There are multiple approaches to the general problem but none will be helpful if your system has special requirements/constraints. – Sean Dec 1 '10 at 21:01
Sorry Sean. I edited the post to hopefully be a little clearer now. I originally didn't include software because I thought it was more of a theoretical question. – DBlack Dec 2 '10 at 7:57
No apology necessary! We're all trying to make these questions/answers more useful for everyone. – Sean Dec 2 '10 at 16:01

I suggest you have one table that contains both the polygon and point data. This table would have (at minimum):

  • an id column that is a foreign key to the matching asset record,
  • a geometry column that contains that polygon geometry and
  • a geometry column that contains the point geometry.

Create a trigger that updates the point column based on inserts/changes in the polygon column using st_pointonsurface.

Create two views, one that has only the polygon columns and one that contains only the point column (include the id column and any others in the views, of course). These views are what you register with SDE.

This way you should be able to worry only about keeping the polygon data up-to-date. If there's no polygon, you can still put in a point. Remember to filter out records with null geometries from the views.

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Now that I read my above question again it looks quite convoluted..sorry about that! I understand displaying different layers at different scales isn't tricky, there are many ways to manage this. I'm more interested how these two layers display the same features relate to the asset management system for e.g. if you then have two layers showing the same feature do you relate one or both to your asset management system? I believe that managing to features to relate to one asset record could be a maintenance nightmare. – DBlack Dec 1 '10 at 20:21
What kind of storage are you using? It all in a RDBMS? Something else? – Sean Dec 1 '10 at 20:56
Its all RDBMS Postgresql/PostGIS. – DBlack Dec 2 '10 at 0:06

I feel like you might have a couple of questions in your question. For the question in your title, your don't provide enough information about your GIS or asset management system to answer.

However, I think this is a good question, but certainly not limited to asset management.

Do I now have to create a polygon layer for my dams to be used with the asset management system for viewing at 1:1,000 then a point layer for mapping purposes when producing a map of the same sites at 1:100,000?

Currently, we have both the building outlines and point features in our Esri geodatabases. We're just starting a Cityworks implementation, but it looks like the point features are what we are using to relate our tables to (since we maintain the point features but the building outlines are maintained by a different agency).

Having both the point and polygon geometries for the same feature isn't uncommon. For Esri geodatabases, these have to go into different featureclasses. You can't mix geometry types in Esri featureclasses (at least not in a way that is recognized by Esri software).

Since you are using an Esri geodatabase, you might be able to use cartographic representations. I haven't used them (until a minute ago), but it looks like it works. In my screen shot, I'm display 1 layer with the building cartographic representation and the 2nd layer with the actual feature geometry. If you apply the scale ranges, you can have buildings change from poly to point symbols as you zoom out. I will say that the user interface for cartographic reps feels less refined than the rest of ArcMap and ArcCatalog.

alt text

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The GIS software is esri based and the Asset management system is mincom ellipse. Sorry for the lack of info, I though it was a more theoretical question. In your example you are using the building points to relate to asset records and vice versa? Do the building polygons have any knowledge of the asset records or are they just there for show? I would imagine that you want a one to one relationship between location and asset? – DBlack Dec 1 '10 at 20:28
We are just starting our implementation, but you are correct: our building polygons will have no asset knowledge. – Jay Cummins Dec 1 '10 at 20:54
I think it would be up to the AMS to handle multiple GIS features per asset although I don't think any do. Or perhaps store multiple geometry fields per GIS feature and display certain geometry at certain scale, but I don't think we are close to that sort of functionality with ESRI geodatabases and software. – Jay Cummins Dec 1 '10 at 21:00

Do I now have to create a polygon layer for my dams to be used with the asset management system for viewing at 1:1,000 then a point layer for mapping purposes when producing a map of the same sites at 1:100,000?

One alternative might be to develop a custom renderer that displays points for dams when zoomed out beyond a certain scale.

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Depending upon scale I would show features differently.

To save of storing multiple geometries for your feature you can use geometric centroids of buildings to compute a single point to represent the asset at much larger scales this will allow you to store single geometries for your assets.

But it does depend on your GIS software as to how this is implemented.

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