Dissolving polygon on QGIS

Question

I have a grid of polygons as in the figure below;

I need to dissolve the polygons into a single feature. I used the Dissolve tool on QGIS without specifying any dissolve field. The QGIS result is shown below;

In the attribute table, there is only one feature but the feature contains multi-parts. Performing the same operation on ArcMap, I got the result below which is the expected output. Still a single multipart feature but a finer polygon with lesser vertices.

Any idea on why QGIS behaves that way and how to get my expected result with QGIS?

EDIT: A link to the layer. https://drive.google.com/file/d/1FY-bmamtvznPKaUPzBrAvyYOf6q_-4VU/view?usp=sharing

Answer 1

First, use "Vector geometry > Snap geometries to layer" tool. Use the grid layer as input and reference layer with tolerance 0.00001. Then, use "Dissolve" tool.

Answer 2

In this specific case it also works to update the geometry using the field calculator:

• expression to use: geom_from_wkt(geom_to_wkt($geometry,6))

then use the dissolve algorithm:

Answer 3

The buffer tool has the option to dissolve the result. Depending on your use case choose a marginal buffer distance.I used 0,0001 degrees and the result is around 12m bigger than your data which seems acceptable with the total extent it has.

Answer 4

OpenJUMP has a tool "Show vertices in fence" that can be used for evaluating what tolerance to use for snapping. For example in this place

the difference in the coordinates of the vertices is minimal

I had a try with QGIS "Snap to grid" tool with a tolerance of 0.0000000001 and that was enough for getting the desired result.