topic Can least-squares adjustments cause gaps between two parcels? in State & Local Government Questions

Can least-squares adjustments cause gaps between two parcels?

ChristinaLindsay1 — Thu, 12 Dec 2013 12:43:46 GMT

I performed a least-squares adjustments on a group of parcels and they turned out great. As I was reviewing my work to touch up on areas that need a little more adjusting I noticed there was a gap between two certain parcels. I had to zoom in close to see the gap.

Can that happen when a least-squares adjustment is performed? Is it possible that I used the transform parcels tools and that is why this happened? I don't remember using them, but that's the only explanation I can think of.

So far, I only see this issue in one place in a group of 2112 parcels. The line between the two parcels is a curve if that makes difference.

Attached is the gap I'm talking about. The imagery is pixelated because I'm zoomed in the area really close.

Re: Can least-squares adjustments cause gaps between two parcels?

TimHodson — Sat, 21 Dec 2013 01:56:38 GMT

Hi Christina,

Here are few things to note and to check.

Note:
When you are zoomed in to a scale greater than 1:1, and the extent of your whole map measures in the 1/100ths of a foot, then you may see this effect: the cartography is not optimized for these highly zoomed in views, especially as your map extents begin to approach the XY tolerance of the feature dataset. This value defaults to 0.001m. There�??s a good help topic on the resolution and xy tolerance; you should not need to change these default numbers.

Check 1:
An important test is to figure out whether or not the geometry operations of GP tools and of the other tools in ArcMap detect any difference/gap. These geometry functions should see these lines as being the same. For example, one test in this case would be to do a select by location, starting by selecting one of the parcels that have the curve, then attempt to select the curved lines based on the �??share a line segment�?� option, as indicated in this graphic:

[ATTACH=CONFIG]30056[/ATTACH]

If both curved lines are selected after this, then the system identified them as equivalent, and the result is as expected.

Check 2:
Take a look at the attributes for each of the curves in question. Do they have different radius attribute values? Also find the radial point location for these curves. (the point at the center of the curve) Does each curve have its own radial point? If the attributed radius for each curve is the same, these radial points need to be merged into a single point that is shared by both the circular arc curves. After merging the radial points re-run the fabric adjustment.

Check 3:
There�??s a tool under the customize environment called Regenerate Fabric that you can use on selected parcels or on the whole fabric (whole fabric if there is no selection.) This tool will let you update the fabric geometry based on the point positions. See the graphic below on info about how to get it: drag the tool onto a toolbar, close the customize dialog, select the parcel, then click this button:

[ATTACH=CONFIG]30057[/ATTACH]

See also the last paragraph in this help topic. Regenerate may not change anything if, for example, the Check 2 test passes the line equivalence test.

-Tim

Re: Can least-squares adjustments cause gaps between two parcels?

ChristinaLindsay1 — Thu, 23 Jan 2014 18:03:52 GMT

Tim,

Thank you so much for your answer. It turns out the curve is really bad and made lot of line segments instead of a true curve with a radius. As I understand, if there are many line segments to create a curve then it is just best to recreate the parcel and join it back to the fabric.

I thought I fixed all these line segments using the Curves and Lines toolbar, but I guess it missed this one.

If I find more gaps in between the parcels in the fabric I'll take your post into account.

Thanks again,
Christina