Re: [transims-developers] Clarification of Data in Snapshot

[Clark H. <cha...@vo...>]

Good afternoon,

     We wanted to follow up with you to make sure you received our last 
email. We are experiencing some difficulty parsing and contextualizing 
some of the data exported from TRANSIMS for the 2020 SMC Data Challenge. 
Please see the quoted text below for more information. Any clarification 
on these apparent outliers in our data would be greatly appreciated.

On 6/18/2020 7:35 PM, Clark Hathaway wrote:
>
> Hello Sponsors,
>
>
> We are a team taking on Challenge 4 of the 2020 SMC Data Challenge, 
> and we would like clarification regarding possible discrepancies we 
> noticed in the traffic simulation snapshot dataset.
>
>
> Specifically, many of the records in this dataset seem to have 
> position data that is inconsistent with both the provided road network 
> and with the actual geography of the Chicago area. We’ve identified 
> three main problems:
>
>  *
>
>     Over half of the records apparently have link offsets (distances
>     travelled) that are greater than the actual lengths of their
>     associated links.
>
>  *
>
>     On top of that, many records have UTM coordinates that lie inside
>     of buildings, on train tracks, in rivers, or are even in Lake
>     Michigan.
>
>  *
>
>     Even when the link offset within a record is valid, it often does
>     not match the UTM position in the record: computing the absolute
>     UTM position of the vehicle from the link and offset information
>     results in positions that can be hundreds or thousands of meters
>     away from the stored UTM position.
>
>
> One specific example of the first problem can be seen in row 55 of 
> file Snapshot_2000000.csv, describing vehicle 34970 at time 7:24. It 
> is listed as travelling down link 1210 with an offset of 202.5 meters; 
> however, link 1210 should only be 14.6 meters long, based on the 
> coordinates provided in the road network dataset.
>
> After taking a random sample of roughly 5% of the dataset (1.2 million 
> records), we found that almost 685 thousand records (or about 55% of 
> the sample) have this problem.
>
>
> An example of the second and third problems can be seen in row 105,310 
> of file Snapshot_4000000.csv, which describes vehicle 34271 at time 
> 9:00. This record contains a valid link and an offset that is 
> consistent with the computed length of that link; however, the given 
> UTM coordinates for this vehicle (16N 447301 4635366) place it in the 
> middle of the Chicago River.
>
> We tried computing a new position for the vehicle based on the link 
> and offset information provided in the record, by using the offset to 
> interpolate between the endpoints of the associated link. However, the 
> position as calculated by this method is 1086 meters away from the 
> position stored in the record.
>
>
> Furthermore, we’d like to ask if parked cars are simulated by 
> TRANSIMS, and if that might cause simulated vehicles to appear to be 
> inside of buildings.
>
>
> Thank you for your time.
>
>
> Sincerely,
>
> Sebastian Mobo and Clark Hathaway
>

Sincerely,
Sebastian Mobo and Clark Hathaway