Drive Time Options

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Go to Options > Drive Time or Drive Distance IsoOptions_32x32

 

The following dialog is displayed which allows you to add, delete or amend the number of zones or the way they look.

 

IsochroneOptionsDLG

 

 

 

The dialog shows a list of zone's added for generation of isochrones. The values reflect either distance or time depending on the choice of shortest or fastest route. Default values are 3 zones with values of 5, 10 and 15.

 

Adding a Zone

When you click on the "Add Zone" button a new one is added to the list. It will always be one greater than the last zone shown in the list.

 

Deleting a Zone

When the user clicks on the "Delete Zone" button, the selected zone in the list is removed.

 

Changing a Zone Border Colour

To use this option you must first select a zone from the list displayed.

By clicking on the button with the line, the user will be able to select a line style in which the border of the selected zone will be displayed.

 

Use style for link isochrones

If you tick this box then the line style used above is used when generating link based isochrones.

 

Changing a Zone Fill Pattern

To use this option you must first select a zone from the list displayed.

By clicking on the button next to the line style button the user will be able to select a fill pattern for the selected zone.

You can have separate styles and values for Drive Time and Drive Distances.

 

Doughnut polygons

When this option is checked then the overlaying polygons are cut from larger polygons. This results in polygons that represent "bands" of time between two values, i.e: 0-5, 5-10 and 10-15. Otherwise 0-5, 0-10 and 0-15 polygons are generated.

 

Smooth Isochrones

This option will remove a lot of the spikiness of the voronoi and polygon isochrones to give them a more rounded look and feel. This do slightly reduce the overall accuracy of the resulting polygons. Also there are some circumstances when using the voronoi type polygons that gaps may appear between polygon vertices. It is up to the user to decide when to use them and when it is inappropriate to use them. Service Area polygons are not smoothed.

 

Normal Voronoi Isochrone

Normal Voronoi Isochrone

Smoothed Voronoi Isochrone

Smoothed Voronoi Isochrone

                                                         

Retain Holes / Retain Island

This option will allow you to alter the look of your isochrones. If you unselect the retain holes option then any areas within the main isochrone that cannot be reached (because of the time or distance setting) is ignored. The same is true if you unselect Retain islands. While this makes the isochrones aesthetically pleasing, it can lead to misleading results and so you use this at your own risk.

 

Normal Voronoi Isochrone with Holes

Normal Voronoi Isochrone with Holes

Voronoi Isochrone with holes removed

Voronoi Isochrone with holes removed

 

Accuracy

The accuracy option will determine how the voronoi drive time boundaries and service area polygons are created. The same settings are used for both isochrone methods and is explained here:

 

During calculations additional nodes can be added dynamically along the links, so long links will get more nodes added, while shorter links will not. You can define the approximate additional nodes to have added compared to the initial number of nodes:

 

Most: 6 times more nodes.

Average: 3 times more nodes.

Least: No additional nodes (default).

Custom: Enter a number corresponding to the number of additional nodes you want (in the same way as above).

 

The larger the number, the more RAM is needed and the requirements increases fast, so don't just type in a very big number.

 

Most – The isochrone will reflect very accurately the extents of the boundaries using every link in the network. This results in very jagged looking boundaries.

Average – This will generalize some of the spikes to produce a smoother looking polygon.

Least - This will generalize some of the spikes to produce a much smoother looking polygon.

Custom - This is automatically set to be the most accurate isochrones possible. The additional nodes do not affect this function in any other way.

 

Use Selective links

You can use this option to control which links are used for generating voronoi isochrones. This can allow you to produce nicer looking isochrones. The images below show the effect of leaving out some of the links:

 

Isochrone using all links

Isochrone using all links

Isochrone with the major road links not considered

Isochrone with the major road links not considered

 

So in the above image you will see that along the major road some small part of the isochrone are generated around its nodes. This can make them look untidy. So if the user tells RouteFinder not to use the major road links unless they form a part of the main isochrone. The result is a nicer, more understandable isochrone.

 

To use this option you would add a smallint field to your network table. You would update all the records to equal 1. Then those links you want to exclude from the isochrone generation you would mark with a 0 (zero).

 

In the dialog you would click on the checkbox to enable "Use Selective Links". Then you pick the column from the network table that contain the 1 and 0's. They will automatically be reloaded the next time the network is loaded if used.

 

 

Clip Polygons

This allows the clipping of polygons to another table, for instance a coastline, and will give a nicer presentation of the result. See the images below to see the difference in the options.

 

IsochroneNotClipped IsochroneClipped

Drive time polygons not clipped  / clipped to the coastline.

 

This setting applies to Drive Time Polygons and Service areas.