MapInfo Pro

MapInfo Monday: Erase Inside and Erase Outside

  • 1.  MapInfo Monday: Erase Inside and Erase Outside

    Posted 10-03-2022 08:28
    Happy #MapInfoMonday.

    We have earlier had a quick look at Erase Outside when we discussed a quick and easy way to perform Proportional Overlay Analysis.​

    In this article, I wanted to highlight the fact that MapInfo Pro allows you to erase selected objects outside as well as inside of one or more objects.

    Imagine this scenario where we have a number of non-overlapping zones along a highway. Around the highway, we have created a 2500 meter buffer zone.

    There are scenarios where we are looking for the zones that intersect or overlap the buffer zone around the highway. This could be if we are looking to understand if a new planned highway will interfere with endangered species. It could also be used if we want to understand the telco coverage along the highway without going into the details of the actual coverage.

    In both these cases we can use the Erase Outside feature of MapInfo Pro to remove the zones that don't overlap the buffer zone along the highway.

    Once we have done this, it's quite easy to do area calculations on the remaining zones.

    The opposite scenario is where you want to remove the zones that are inside or overlapping the buffer zone. This is typically used when you are looking for a specific site that needs to meet certain criteria. One criteria can be expressed by a distance to existing infra structure or populated areas. Maybe you are looking for locations to build new wind mills but they need to be 2500 meter, or any other distance, from highways or populated areas.

    With the erase feature in MapInfo Pro, you can remove these areas from the potential locations.

    No matter which process, you are looking to do, the process is the same.

    First, you need to make the layer with the non-overlapping zones in our example editable.

    Then you have to select all records from this layer. You can quickly do this through the context menu on the layer.

    And now, set the selected zones as the target for the next operation using Set Target on the Spatial tab.

    Now you need to select the object or objects you want to use as your cutting object. In our case it's the buffer zone around the highways.

    With this object selected, you can now activate the ease method of your choice - Erase Target or Erase Outside Target - from the Erase dropdown on the Spatial tab.

    The Data Disaggregate dialog can help you mange how the data is transferred from the original objects to the objects erased.

    In MapBasic we have two functions that can hep you do the same. Erase() can be used to erase part of one object that intersects another object. Overlap() on the other side can be used to erase part of one object that doesn't overlap another object. These function could for example be used in a join between two tables.

    For what use cases are you using the Erase or Erase Outside features of MapInfo Pro? I would love to hear about those.

    Peter Horsbøll Møller
    Principal Presales Consultant | Distinguished Engineer
    Precisely | Trust in Data