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UK Safety Camera Database Duplicates

 
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mountain
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Joined: 18/09/2002 09:32:57
Posts: 54
Location: United Kingdom

PostPosted: Sun Sep 14, 2003 8:04 am    Post subject: UK Safety Camera Database Duplicates Reply with quote

I have been noticing that as the database gets updated there are more and more duplicates appearing. For instance GATSO:1260, GATSO:931, GATSO:1259 all refer to the same camera. GATSO:1260 and GATSO:1259 are approx. 170 yards apart. There are more duplicates that I have noticed on the A2 and A40 and others that I forget.
I was wondering if there was any way to delete any within say 200 yards of each other, I imagine most people don't need separate warnings for cameras that actually are closer than that.

Piers

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longitude
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Joined: 14/07/2003 13:42:15
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Location: St Albans, Hertfordshire

PostPosted: Sun Sep 14, 2003 8:04 am    Post subject: UK Safety Camera Database Duplicates Reply with quote

I've only used poi to warn about cameras once, very impressed though. My experience was that I was warned about two cameras that were very close together to catch speeding motorists in both directions, but of course only one applied to me. Is that perhaps what's going on in your examples? As things stand the software can't disable a warning about a camera that applies to traffic going the opposite direction.
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mountain
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PostPosted: Sun Sep 14, 2003 8:04 am    Post subject: UK Safety Camera Database Duplicates Reply with quote

In some cases that is the case but in others there are definitely duplicates, my example above for instance. However, my point was that if there are 2 cameras within close proximity of each other (perhaps on opposite sides of the road) having both in the database is actually unnecessary because a single warning would draw my attention to both of them (or if not both, definitely the one that applied to me).

Piers
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Dave
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Joined: Sep 10, 2003
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PostPosted: Sun Sep 14, 2003 8:04 am    Post subject: UK Safety Camera Database Duplicates Reply with quote

There have been a lot of duplicate cameras that have been erroneously added due to the software we're using, Duncan is currently working on this for the next release to remove these entries.
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Oldie
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Joined: 22/11/2002 13:33:48
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Location: Surrey, UK

PostPosted: Thu Sep 18, 2003 2:39 pm    Post subject: Re: UK Safety Camera Database Duplicates Reply with quote

mountain wrote:
I have been noticing that as the database gets updated there are more and more duplicates appearing. For instance GATSO:1260, GATSO:931, GATSO:1259 all refer to the same camera. GATSO:1260 and GATSO:1259 are approx. 170 yards apart. There are more duplicates that I have noticed on the A2 and A40 and others that I forget.

I was wondering if there was any way to delete any within say 200 yards of each other, I imagine most people don't need separate warnings for cameras that actually are closer than that.



Piers





Piers,

This is a repeat (and expanded) posting of two that I put up on the old website - as Dave has said elsewhere, there was a cut-off when a dump of the forums was taken so some replies have been lost.

You can use my program POIManager, which is available in the Downloads area, to remove duplicate entries found within a radius that you can select from a range of values. So you can tailor the PocketGPS safety camera database to meet your own requirements. As Dave has said, there was an error in the program which allowed some duplicates, within the 20 metre radius used by PocketGPS, to get through the checking.

Deciding on a radius to use is tricky, because you may want to be aware of cameras on different sides of a dual carriageway. On the other hand how accurate are our recorded positions, when do you press the record POI button?

I have run POIManager on v 1084 of the PockGPS database and obtained the following results

Match radius (metres): No. of POI using 20m - > No. of POI using new value
20: 2742 -> 2724 (there were 18 entries allowed through by mistake)
50: 2724 -> 2509
100: 2724 -> 2362
250: 2724 -> 2157
500: 2724 -> 1860

You will not be able to select the 250 metre match radius as I have added it in my new version which I will release soon. However, I have noticed some differences in the final number of cameras when using POIManager in different ways - this I will have to investigate Sad

Compiling a new version of the database is a very onerous task and we should certainly thank PocketGPS, and Duncan in particular, for all of the effort that is put in on our behalf.

Many of the duplicates within say a 50 metre radius are due to inaccuracies in the original database, but if we keep sending in our recorded camera positions then the quality of the database should improve.

Richard
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DavidW
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Joined: 17/05/2003 02:26:21
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Location: Bedfordshire, UK

PostPosted: Thu Sep 18, 2003 8:18 pm    Post subject: Reply with quote

My last post on this subject was lost too.

My point was, in essence, that there are some cases where cameras are genuinely close together. I came across one site recently where there was a truly bidirectional Truvelo installation - one camera on each side of the road about 5 to 10 metres apart.


I have resurveyed an area that was full of errors - the A41 Hendon Way in London, but sadly my corrections haven't made it into the Pocket GPS database yet. The worst two, I think, are just as this road becomes the Finchley Road. For the life of me, I can't see what has been identified as GATSO 961, and GATSO 962 (a red light camera) is shown something like 20 yards off the road! My resurvey continues right down the Finchley Road to Lords.


All that said, the database is a wonderful achievement - one for which I am very grateful. It's very hard to maintain such a database.



David
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MikeB
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Joined: 20/08/2002 11:51:57
Posts: 3859
Location: Essex, UK

PostPosted: Thu Sep 18, 2003 9:34 pm    Post subject: Reply with quote

I suspect that the duplicates creep in due to the way poeple (and equipment) record the cameras. Nobody is going to stop and make sure they have a great fix then record it. When you see a camera that isnt in the database you hit record.

The problem is where do you record? Some people seem to record at the camera's physical location, some at the index marks on the road. Even given those differences the delay (human and PDA/GPS) in actually making the recording can vary greatly.

I have seen some cameras recorded 4 times check the A127 heading towards Southend. I think some people hit the record button as soon as they see a camera they are that far out.

Bottom line I suppose is to try and identify the duplicates for the next database release, and then make manual camera deletions if that fails.

The problem with increasing the tollerance for duplicates is that some genuine ones will be removed. Again in Southend there are cameras at the same location either side of a dual carriageway, but within 50 yards of each other.

Slightly off topic there are some genuine installations where 3 camersa are installed within 50 yards of each other. The roadworks on the A12 near Witham have 2 sets like this.
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Mearns
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Joined: 24/08/2003 18:17:58
Posts: 162
Location: Aberdeen, Scotland

PostPosted: Thu Sep 18, 2003 11:52 pm    Post subject: Reply with quote

Over the past week I've driven from Aberdeen to Torquay and back, having only had my iPAQ 2210 for a few days, so this is my first experience of the excellent camera database.

Unfortunately I couldn't get my Checkpoint sound files to play so the only warning I had of speed cameras was a visual one, but there were unfortunately masses of duplication and erroneous camera sites. Is it worthwhile asking people only to press the record button as they pass a camera on the same side of the road as they are travelling? - so often on a dual carriageway cameras were shown on both sides of the road as though people had seen the camera from the opposite side and recorded it.

From this journey I now have 7 unlisted sites recorded, would have been more but for my newbie fingers messing up - how do I get them out of Checkpoint and into a file to send in by email? Is it purely a case of copying them manually and putting them into POIManager or what?
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Mearns
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Location: Aberdeen, Scotland

PostPosted: Fri Sep 19, 2003 5:52 pm    Post subject: Reply with quote

Sorted the query in the last paragraph of my post above - email with 7 cameras on its way shortly.

Tony
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mountain
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Joined: 18/09/2002 09:32:57
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Location: United Kingdom

PostPosted: Sat Sep 20, 2003 12:43 am    Post subject: Reply with quote

Richard

Thanks for your reply. I hadn't realised POIManager could do this, I had thought it was just for finding duplicates between master file and update file. I think I shall try removing all duplicates within 100 metres of each other and see if the data is still usable with my set up.

Thanks

Piers
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