Guide to Working with Map Shapefiles in Ortelius

Ortelius 2 supports import and georeferencing of multiple shapefiles. This can be a powerful way to start your next map, but it can sometimes negatively affect performance or produce unanticipated results. This guide will help you understand key features and limitations of working with shapefiles in order to achieve the best results.

How To Achieve Best Performance & Results

  1. Use shapefiles designed for cartography.
  2. Simplify your shapefiles.
  3. Limit the number of objects in your source shapefile.
  4. Extract your area of interest before importing data-heavy shapefiles.
  5. Limit your selection of multiple objects.

1. Use Shapefiles Designed for Cartography

Shapefiles are most often created and used by geospatial/GIS professionals for data analyses and data management. For these purposes, professionals often strive for the most detailed, accurate data possible.

The problem: Map design needs pleasing visual presentation, and map-makers need to fit large areas of the earth onto relatively small maps. Therefore, GIS shapefile data are often too detailed to work well for cartography. High-detail data also place a heavy processing burden on vector drawing programs, affecting performance.

We use Natural Earth Data. We’re also proud contributors to this open source project.

Natural Earth Data solves a problem: finding suitable data for making small-scale maps. In a time when the web is awash in geospatial data, cartographers are forced to waste time sifting through confusing tangles of data to make clean, legible maps. Natural Earth is a convenient solution that works well with Ortelius.

Neatness Counts. Natural Earth’s carefully generalized linework maintains consistent, recognizable geographic shapes at 1:10m, 1:50m, and 1:110m scales. Natural Earth was built from the ground up so you will find that all data layers align precisely with one another. For example, where rivers and country borders are one and the same, the lines are coincident.

2. Simplify Your Shapefiles

The problem: What do you do if you have shapefiles that need simplified?

We use Ortelius and mapshaper.

Ortelius solves a problem: Simplifying your shapefiles during import in Ortelius. Choose ‘File > Import Shapefile’ and click the ‘Options’ button at the bottom of the import window. Check ‘Simplify’ and choose the level of Douglas-Peucker simplification. Ortelius does not provide interactive simplification.

Mapshaper solves a problem: Interactively simplifying your shapefiles before import in Ortelius. Mapshaper is online software for editing shapefile and several other data formats to generates simplified shapefiles suitable for use with Ortelius. It is an open-source project. See the project wiki for more documentation on how to use mapshaper, particularly these Tips for Importing Shapefiles. In addition to mapshaper, some GIS software have their own simplification routines.

HINT: Mapshaper works in recent versions of Chrome, Firefox, Internet Explorer and Opera. Exporting is not supported in Safari.

3. Limit the Geographic Area and Number of Objects in Your Source Shapefile

The problem: Shapefiles can cover large areas, but your area of interest is much smaller. For example, you receive shapefiles from your city but you are interested in a neighborhood.

We use Ortelius and qGIS.

Ortelius solves a problem: Extracting your area of interest before importing data heavy shapefiles reduces the geographic ares and number of objects in your map. This is an important topic covered in more detail below.

qGIS solves a problem: Pre-processing your shapefiles to save only selected features reduces the geographic ares and number of objects in your imported shapefiles. qGIS is an open source GIS software that runs on the Mac. It is full-featured and powerful, though sometimes installation can be a bit trying. This valuable tutorial explains how to import a shapefile, change its coordinate reference system (CRS) properties, select features, and save selected as new shapefile.

HINT: qGIS is profesional GIS software. We recommend this workflow only for advanced users.

 

4. Extract Your Area of Interest Before Importing Data-heavy Shapefiles

The problem: The area of a shapefile is larger than your area of interest, and the dataset is heavy with too many features.

We use Ortelius’ Extract Slice To New Document.

Ortelius solves a problem: Extracting an area on your map grabs features of interest and discards the rest. The map projection/CRS properties are remembered in your new document. When you import another shapefile, Ortelius only imports those features that are coincident with your new area of interest. Watch this video to see it in action.

Use the ‘Slice’ tool to draw a slice around your area of interest. With the slice still selected, choose ‘File > Extract Slice As New Document’. Features within, or touching, the slice area are extracted. The rest of the features are discarded. Resize your new document, then use ‘Reposition’ to resize and reposition your map features.

5. Keep Actions Small – Limit Your Selection of Multiple Objects

The problem: Shapefiles were created to use in geographic information systems (GIS) which render objects on-screen in raster and store attribute information in efficient databases. Ortelius renders objects in vector and attribute information is object-oriented (not in a database). Rendering hundreds to thousands of vector objects, or performing actions on their object attributes, is an intensive operation. Unlike rendering object in raster, rendering in vector means every point and curve of every object must be calculated on every draw. Maps heavy with vector objects and attributes can experience seriously performance issues.

When working with large files, we are thoughtful about keeping our data, and our actions, small.

Small actions help reduce performance issues: For example, try to limit selection of many objects at a time (selecting hundreds of objects at once can affect performance).

Map Projections, CRS, Georeferencing and the “First-In” Rule

Ortelius uses a “first-in” rule to set the document’s coordinate reference system (CRS). Shapefiles of the same projection are now georeferenced on import. This means when you import multiple shapefiles with the same projection/coordinate reference system (CRS) the layers will properly align.

We use qGIS and rely on source data providers.

Source data providers solve a problem: Providing shapefiles that have consistent map projection/CRS settings. Often (but not always!) data providers will apply the same CRS for all their shapefiles. Sorry, we cannot assist you with reprojecting your data.

qGIS solves a problem: Pre-processing your shapefiles to share the same CRS in your imported shapefiles. qGIS is an open source GIS software that runs on the Mac. It is full-featured and powerful, though sometimes installation can be a bit trying. This valuable tutorial explains how to import a shapefile, change its coordinate reference system (CRS) properties, select features, and save selected as new shapefile.

HINT: qGIS is profesional GIS software. We recommend this workflow only for advanced users.

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