I am digitising road lines and symbology this week. There are over 10,000+ items in this dataset that is being manually digitised as linear referencing causes too many errors. In this article I'm documenting the workspace, procedures and notes.
Dictionary: Transverse Lines
For the purpose of this article I should explain the dataset I'm working on.
Hawkesbury City Council maintains road line markings and symbology for all local roads. This includes anything that's marked on the road from holding lines, zig zag lines, centerlines and pedestrian crossing symbology.
Tranverse lines are a category of road lines defined as any marking that cuts across the direction of the road. So holding lines and zig zag lines fall into this category. As you can imagine there are a shit load of road lines to maintain which is why we want to map them in a spatial information system.
I've been supplied with a table containing the AssetRID, Asset Description, Road Name, Road Segment Number, Road Side, Suburb and Starting Chainage. The job is to digitise all these records into the corporate spatial information system.
In Microsoft Excel it's probably useful to create two additional fields. One field is
Status which would be used to track whether a record has been digitised or checked. In this field I usually use Y = Yes, N = No. The second field is
Comments which can be additional comments about the asset or record if required. It's useful to know why you didn't digitise that record (like if you can't find it on the aerial or verify through a site inspection). The data supplier can then rectify the issue.
If you're not familiar with the function
Freeze Panes, go look up how to do it.
Lastly learn to use
Data > Filters because it saves you time looking up records. You can really drill down a large table to just the records you're looking for based on the values you're interested in.
For example I only want "blank records" in
Status and "TRANSVERSE LINES" in
Asset Short Description and the first road name on the list under
Street Name and Excel will filter out the rest of the data as I work down the list.
Once the asset has been digitised I place a "Y" under
Status and the spreadsheet will filter out that record.
If you want the record back, just clear all the filters.
Managing Data In ArcGIS
You may want dual monitors for this workspace. If you only have one, then your display will be cluttered with information panels. Monitors are cheap and most GPUs will handle two screens with no problems. Three screens will be optimal if you don't want to alt tab to see the source table! (Fat chance my employer will give me three!!)
So the top three panels are the
Table of Contents,
Create Features and
Identify Attributes. You want these three when you're editing a feature in ArcGIS. Make sure you make the feature class "Tranverse Lines" the only one selectable if you don't want to mess up the underlying layers.
The bottom panels I normally reserve for tables. You can filter what fields are shown through layer properties. In this screen I have both the Roads SMEC table and the Transverse Lines table open. The reason is because after I run a selection by attributes, I want to zoom to the road line segment from the table view. Then in the map view I create the feature, and the table for
Transverse Lines will appear adjacent to the road layer I'm working off. It's also one less click when I'm going through 10,000 records!
PS: SMEC is a company we sourced road data from. You'll be surprised how long it took for me to realise what SMEC meant. It's not glaringly obvious when you're just looking at datasets without the corresponding metadata.
Moving Panels in ArcGIS
If you're wondering how to create perfect layouts, ArcGIS lets you move your toolbox panels and snap them together like Lego. Just click and drag the panels around over the top of another panel and you get the overlay appear like above. The arrows mean you're snapping the panel to the top/bottom/sides and the centre blob is to put the panel on top of the existing panel (which creates the tabs).
Spatial Query: Road Name and Segment
There are two ways to find the location of a road line or symbology. Firstly by the road name and segment number. The second method is by road name and chainage. The Roads SMEC data contains the centreline of a road digistised over the aerial photograph. The segment is numeric chunk of the road. The chainage is the distance from the start (or datum) of the road centre line i.e. 1000 metres from the start of the road.
I use both methods. Segment to narrow down to the chunk of road, and then the chainage to find the exact location of the asset on the aerial photograph. For longer roads greater than 5 kilometres you should use both methods as panning around the screen is inefficient!
Editor (I'm assuming you've created the feature class and template so it's ready to go).
Go to the
Create Features panel and start drawing with the
Straight Segment tool. If the road curves then use the
End Point Arc Segment tool.
Find the asset and trace over the holding line.
Update the attributes that correspond to the supplied asset register.
You pretty much use copy+paste from excel to table view. You could also paste it in the attributes panel if it is quicker (especially for features in the SDE)
Remember to save the changes.
You could get fancy and zoom in to make some complex segments. This one consists of a straight segment plus a slight curve.
This concludes this tutorial.