Latest Contributions by DQ

Hi, the data represents a river system with tributaries in a catchment. All polylines. Rivers are made up of reaches, i.e. a section of the river with a particular characterization, eg Reach/Stream condition - Good, Moderate, Poor. Reaches are connected at their endpoints to the next reach along the river, except for tributaries. Tributaries flow into main branches, connecting at their endpoints to somewhere along the polylines of the main branch. Tributaries are always separate reaches. The original data comprised many reaches, which when dissolved, combined reaches that connected at endpoints, but tributaries formed their own dissolved reaches. My goal is to select Moderate reaches which lie between 2 Good reaches (see Reaches GoodModPoor). This time I  used Spatial Join/Intersect Then  to filter I used GoodMod_SpJn, and selected by attribute. a) see Reach Condition#1 - select Stream condition -  Moderate,Moderate - selects all items. b) see Reach Condition#2edited - select Stream condition_1 - Good,Good, it selects a variety of reaches, some connected to 2 good reaches (marked A), others to 1 good, and 1 poor at the other end (marked B). So getting closer with your help, and understanding it more, but not quite there yet! I really appreciate your assistance. All data is from the one dataset, using same Coordinate System GDA1994NSWLambert ... View more

Hi David, thank you for your advice. It was helpful but still have some issues. The goal is to extract any Blue (dissolved) segments which connect at both ends to Green segments, i.e find all the Green-Blue-Green. Yes, there are segments which come in from the side (stream tributaries) but they are not causing the problem. Dissolving (unsplit checked) the segments worked well. Then tried Intersect on Green (dissolved) and Blue (dissolved) but that didn't return any results. So then created layer Blue-Blue connected reaches, selected by location (boundary). Then erased from Blue (dissolved), which should have left just Blue reaches which fell between two Green reaches. However, still some Blue-Blue reaches were included. It appears that the dissolve did not fully work initially? Also tried Select by Location (within distance, varying meterages eg 50m, 100m), but still unable to get a clean set of Green-Blue-Green. Is my logic sound? Is there an easier way? I would really appreciate some advice, kind regards ... View more