GIS Distance Data¶
In some applications, there is a wizard question if distance and duration data should be retrieved from a third-party provider (Location IQ). If this option is activated, the page GIS Distance Data become part of the workflow. The purpose of this page is to help the user inspect the distance and duration obtained from the external service.
In order to use this, you need to set attribute Retrieve Distance in sheet Transport Cost Data to indicate for which lanes you want to generate the distance and duration.
Once you open this page, you see the list of transportation lanes for which the distance and duration is needed. The data is retrieved once you click on the page action Retrieve Distance and Duration for lanes. Once you have inspected the results, you need to save them via the Save Distance/Duration Data page action menu. This saves the data so that it can be retrieved the next time you are loading this Excel file.
Distance and Durations¶
After the model is solved, you see four new columns:
Distance: The distance in miles or km, depending on the setting of the wizard. The actual unit is also mentioned in the table header.
Duration: The duration in hours, which is scaled based on the Average Speed, see below.
Speed: This speed is calculated as Distance divided by Duration.
Status: If everything went well, this value is Ok, but other possible statuses are:
No coordinates for Origin/Destination: Either the origin or destination is not geo-coded.
Unable to calculate: There is no route between the two locations. (For example, you get this error if you try to calculate the distance between Europe and the USA.)
TooBig: Location IQ can only handle routes up to 10000 km (6213 miles). If the straight-line distance between origin and destination is larger than 10,000 km, you get this message.
Rate Limited: There are daily limits on your account. If you get this message, save the results that you already have and try the rest tomorrow.
If distance and duration are not successfully generated, but you still save the data, the applications will use a straight-line distance instead, with the specific wiggle factor. In case you set the option not to use straight-line distances, the model will gave a data validation error and prevents you from saving the data.
This map shows the connection between origin and destination (the actual distance is represented on the map as a straight line). This might help to better understand the distance of a particular lane.
The geo-coding service provides both distance and duration data. The distance data can be used directly, there are very few choices/assumptions made to get this data. Once you have determined the route, you know the distance. However, there are many choices/assumptions with respect to the duration. What vehicle is used? Do you drive below, at, or above the speed limit? How busy are the roads? All these questions influence the duration. In the table on the right, you see this average speed as Avg. Speed from Raw Data. However, this might be too low or too high compared to the speed of your fleet (by transportation type).
Therefore, if you provide Target Speed, Data Navigator and the applications will scale the durations such that the average speed of all these lanes matches the Target Speed.
If you change the Target Speed in the UI, this will be saved as part of the dataset. However, you might also want to change that value in the "Transportation Type Definition" in the column "average speed" for the mode of transport, as this becomes the default target speed, so that you do not have to change that the next time you load this Excel.
As mentioned before, it is important to click the Save Distance/Duration Data* page action, so that this data is stored. Only after you click this, the page will get the completed check-mark in the workflow.