ESRI streetmap data for distance calculation.

[jp]

Hello,

I am working with ESRI streetmap data i.e. SDC data is in GCS_North_American_1983. I am also using the streets network dataset provided with the streetmap data which is also in same geographic coordinate system.

I am performing network analysis(OD matrix) in an ArcEngine application and when testing smaller roads shapefile, I projected it to get right distances. 
My question is wouldn't the results be right if the network dataset was built from a projected streets layer. The results would definitely vary if a projected network dataset was used. So should I create a shapefile from the SDC streets file, project it to North America Lambert Conformal Conic and then generate a network dataset.

Or does the ESRI network dataset give right results as it is.

Correct me if my analysis is wrong?

Thanks

[jp]

Hi Alan,

When creating a network dataset in ArcCatalog if no cost attribute is created, user is prompted if a length attribute should be created. This is when the USA roads layer(GCS, shapefile) doesn't have a length field.  But when creating a Network Dataset in ArcEngine application, I am creating a length field on the fly and calculating field values based on shape. This length field is used to create and build a network dataset on the fly.
These length values differ based on projection(NAD_1983_Great_Lakes_and_St_Lawrence_Albers,North_America_Lambert_Conformal_Conic) of the shapefile.
Even if it were in GCS_North_American_1983 the values differ. To make these values consistent can network dataset be created on the fly like in ArcMap without length field to avoid discrepancies?

Thanks,
Jhansi

[jp]

Hi Alan,

Thanks for the detailed explanation for both my posts. I try creating a network dataset in ArcEngine application with shape field to eliminate length calculations.

I'll test this and will let you know.

Thanks again,
Jhansi

[jp]

Hi Alan,

I got busy working on other stuff so I couldn't test this sooner.

I just replaced the [Length] with [Shape] which worked perfectly in creating a network dataset without length field.

Thanks to you!

[SeanTrench]

I am trying to create a route network model to determine a route for a marathon race. Can you give me any suggestions on how to determine a loop 26.2 miles in length?

[JaySandhu]

It's not straight forward to do this as you in a real marathon course, you need to have permissions on roads to close, have enough width, avoid certain places, go by some historic landmarks, avoid interstates, etc. Given that, you can imagine plopping down some points in a circle of circumference 26 miles (or a circle of radius 4 miles) and on the route layer properties turn on "Reorder stops to find optimal route" and un-check the preserve first and last stop and solve. Look at the length of the route returned and if not 26.2 miles, add some more stops to get the desired length.

Jay Sandhu

[SeanTrench]

Jay, thank you. I'll see how that works. I appreciate the help!