Erro de topologia inválida ao executar BetterBusBuffers

DavisTurner

Sou relativamente novo em GIS e estou tentando fazer uma análise de frequência dos serviços de trânsito da Bay Area com BetterBusBuffers. Tenho usado a ferramenta "Count Trips in Polygon Buffers around Stops" e criei um conjunto de dados de rede apenas com uma classe de feição de ruas para usar a ferramenta (anteriormente tive erros de construção com meu conjunto de dados de rede quando estava usando classes de feição de dados GTFS stop, então removi todas exceto a classe de feição das ruas e isso resolveu os erros de construção). Também tive problemas com o conjunto de dados de rede relacionados à geometria vazia, mas resolvi removendo meu atributo de hierarquia. Após executar a ferramenta novamente, ela falhou após 8 horas com o erro 160196, "topografia inválida." Alguma sugestão de como corrigir? Meu tamanho do buffer foi definido para 20 minutos de caminhada, e usei uma restrição de rede para caminhada também. Meus dados GTFS pré-processados contêm GTFS para cinco agências diferentes, o que acho que está causando o longo tempo de processamento. Já verifiquei e reparei a geometria, e a classe de feição das ruas foi copiada para o geodatabase no qual meu conjunto de dados de rede está baseado.  <\/P>

Melinda Morang

Hello @DavisTurner. First of all, you did the right thing in removing your GTFS data from the network dataset. BetterBusBuffers is about measuring access to public transit, not about measuring access to other facilities by public transit. Thus, you don't want your network dataset to model travelers taking public transit, you just want to model them walking.

 

Second, the size of your GTFS data is probably not the issue.  The Preprocess GTFS tool does the heavy lifting and reads in all the data from the different agencies. Once it's passed that point, constructing the Service Area polygon buffers becomes the difficult part. It will definitely take longer if you have more transit stops, but anyway, the slowness is in accounting for overlapping polygons and trying to "flatten" them.

 

Regarding your error: Are you getting this error on the "Step 1 – Preprocess Buffers" tool? That seems more likely, but please let me know if my assumption is incorrect.

 

This tool can often be finicky, and it's because it's doing some fairly complex geometric procedures to handle the overlapping polygons. Something strange is happening under the hood, and it's kind of impossible to know why. The only thing to do is to try again by altering some of the settings to change the geometry of the resulting polygons slightly and hoping that the geometry error will be avoided. Here are a few things you can try changing to see if it avoids the problem:

• Change the Polygon Trim setting to a different value.
• Update your impedance attribute slightly, like changing the assumed pedestrian walk speed by a small amount.
• Changing the Buffer Size from 20 minutes to some other number (I know, not ideal...)
• This last suggestion applies only if you are using ArcMap and not ArcGIS Pro: Calculate a Service Area Index on your network dataset. Basically, we introduced a newer, better algorithm for creating Service Area polygons which fixed a lot of weird geometry problems and made all-around better polygons. This is the default in ArcGIS Pro, but if you want to use it in ArcMap, you have to explicitly choose to calculate a Service Area Index in your network dataset settings. You just have to check on the check-box and run Build Network again.

 

Note: If you are not using ArcGIS Pro, I recommend switching to Pro anyway to get overall better functionality. The tool might take less time to run or at the very least be less likely to run out of memory.

 

Hope this helps!