0

I'm drawing a geological map so I've several polygons in a single layer as geological units. After finishing the map I need to add a few new geological units (means new polygons), but they are all overlapping one or more existing polygons.

If I draw a new polygon by "duplicate and digitize" tool or not the polygon is always going behind the existing polygons. Otherwise I tried to do by "add ring" on a single polygon there is no problem but if it comes across overlapping more than one polygon at this time "unknown error occurred" message displays.

enter image description here

nmtoken
  • 13,355
  • 5
  • 38
  • 87
Sedat
  • 29
  • 4
  • 1
    Add a tag showing what GIS software you are using – BERA May 11 '20 at 11:59
  • is the question just that you want the green polygon to be on top of the others? if so just drag and drop it to the top in the layer panel – Leo May 11 '20 at 12:09

1 Answers1

2

In case you are using QGIS, there is an option to tell the layer the order in which the objects should be drawn. Probably ArcGIS has the same functionality.

In the layer styling panel you find it at the bottom: open layer-rendering and than click the checkbox "control order of object drawing" (or how it's called in english, see screenshot). Click the icon A-Z and a dialog-window opens where you can select an attribute field that defines the order in which the layers shold be drawn: you can change between ascending and desending.

For the purpose of illustration (see screenshots), I used the id for sorting - however, you can use everey attribute-field or create an own field "layer_order_no" where you can manually define the order of your fields.

Choose a decimal number as fieldtype, so you can introduce a value in between to numbers. If you have field-values of 4 and 5 and suddenly realise that there should be one in between, you can set it to 4.5, adding even more values at 4.1, 4.2 and so on - using an integer, you have to manually change all values accordingly.

Screenshot: descending order: first, the highest value (4: the yellow one) is drawn, than the next smaller no. (3: the green one), going to the next smaller value (2: blue) and finally the smallest no (1: violet) - that's why violet is on the top and the yellow one is invisible (covered by the others): sort descending: 1 an the top, 4 (yellow) on the bottom, not visible here

Screenshot for ascending order: it starts with the smallest value (1: the violet one) - that's why this is now at the bottom, covered by all the others. Than QGIS goes an to draw no. 2 (blue), than 3 (green) and finally it draws no. 4, the yellow: this time, it's the last drawn and thus on the very top!

sort ascending: 4 (yellow) on the top, 1 (violet) on the bottom

Babel
  • 71,072
  • 14
  • 78
  • 208