If you upload a route from your GPS, you may find that the route shown on the OS 1:50k map is a little inaccurate in places. Equally, if you create a route on the Google map you may find that the corresponding route on the OS 1:50k map is also off. This is probably best illustrated below:
The route shown was uploaded from a GPS unit - I was riding on the road at all times. The left hand map is the OS 1:50k Landranger map. You can see that the route is a little off - particularly near the top left corner. The middle map shows the same route displayed on the Google map. Accuracy pretty good. The right hand map shows the OS Street View map. The accuracy of these seem good as well.
I think the definitive answer to this issue was provided by someone on the CTC forum:
OS 1:50k maps are deliberately distorted in places, in the interests of clarity. Roads can be drawn up to 50m away from their true positions.
As they are raster maps, a bit of road is always the same width in ground metres, regardless of the display scale, and the drawn width will be considerably more than the true width. As examples, a single carriageway red A road is drawn at a scale width of about 40m, when it's actually only 7m, and a 4-5m wide white residential road will be drawn at a scale width of about 30m.
If you get several features close together, all drawn larger than their true size, something has to give. Eg a residential road sandwiched between an A road and a railway line. The choice is to either miss something out, draw things smaller, or to draw standard sized features in the wrong place.
Google maps etc are vector maps. There is a single accurate position for the centre of the road, and that's where the road is displayed. How the roads are displayed depends on the scale at which the data is being drawn. It may be decided not to show some of the data at all, so you don't see residential roads when you are looking at a whole city for example.
This raises a good point about all courses. Courses created from uploaded GPS traces will usually be more accurate than mapped courses. Courses mapped on the OS raster maps will be less accurate than courses mapped on the Google maps. If you are using a mapped course in your GPS unit then be prepared for a little inaccuracy.
The OS maps are provided free of charge by the Ordnance Survey Agency. They impose a restriction on the number of map tiles they provide per day. Once this restriction is reached there will be no OS map displayed. Come back tomorrow.
The following comments apply only to drag editing in follow road mode (i.e. route dragging).
It's important to realise that drag editing on bikehike works a little differently to some other bike routing sites. It works the same as Google maps in that when you drag a point it will recalculate the route between the two nearest hardpoints. If you have no hardpoints then the whole route, from start to finish will be recalculated.
So, if you have a 100 mile route (with no hardpoints) and you do a drag edit to correct some problem in the last mile then the whole route will be recalculated from start to finish (passing through your drag point). This may not be what you intended.
If you want to control the extent of the drag editing then add hardpoints (ctrl-click on the route while in drag edit mode). Hardpoints are shown as black dots visible while in drag edit mode. If you drag a point between two hardpoints, or between a hardpoint and the start or end, the drag edit will be restricted to that segment.
Going back to the 100 mile route example above, if you place a hardpoint near the end then drag edit between that hardpoint and the end, then the rest of the route will not be changed by the drag edit operation.
Please also see the help item on drag editing here.
The database is intended to be a public repository of routes to be shared with all users. If you want to save a route as a private route then download it as a GPX and save it to your hard drive.
The elevation data is provided by the GeoNames web service. If for any reason this web service is unavailable then no elevation data will be shown. If this web service is slow to respond then the elevation updates will be slow.
If the supply of elevation data dries up during the creation of a course, the last good elevation received is used as the current elevation. This leads to the flat patches shown below.
There is now an elevation data repair script. This runs overnight and attempts to identify any routes with missing or corrupt elevation data. For each route identified it will re-query the elevation data and insert it into the database. For example, the corrupt elevation trace shown above was corrected to the trace shown below.
So - if your elevation data goes bad while creating a course, check again the following day. It should be corrected. If it is not, it is possible that the script has missed it. Drop me an and I'll make sure it gets corrected.
You can edit either your own or somebody else's course. If you edit somebody else's course and save it to the database then a duplicate of the course (with your changes) will be saved. Please consider whether this is worthwhile as no-one wants a load of duplicate courses in the database.
If you edit one of your own courses and save it to the database then the new course will overwrite the old.
To edit a courses first load the course, then make some changes, then save it. You can change the course track (using drag editing), add or delete POIs, add or delete coursepoints, change the description, change the category and change the source. Currently if you change the course name then a duplicate course with the new name will be saved - even if it is one of your own courses.
If you have courses in the database that were saved before the log on facility was available (and therefore have no owner), send me an email with your user name and the IDs of the courses and I will associate you with these courses.
To delete a course first log on. Then use the "Find my routes" search option to find your courses. Click the delete checkbox to delete the course. Note - you can only delete your own courses.
If you convert a tracklog file to GPX using GPSBabel, and then upload the GPX file to this site, you may get a corrupt looking route, as shown in the left hand image below.
The correct route is shown on the right; this has been uploaded directly as a trl file.
The problem is that GPSBabel (versions 1.3.4 and 1.3.5 beta) seems to assume that the trackpoints in the trl file are ordered sequentially. This is not necessarily the case. There is a further layer of processing required to stitch together the trackpoints in the correct sequence. Therefore, if you want to upload a tracklog file, please upload the raw tracklog file - don't convert to GPX first.