Je dois imprimer à une échelle précise avec exactitude dans ArcGIS Online

Question

Je suis analyste SIG pour une administration locale. Nos données sont au système State Plane. Je dois créer une application dans ArcGIS Online pour imprimer des cartes cadastrales avec des mesures et une impression précises. La projection Web Mercator présente un décalage de plusieurs pieds. Je peux créer l’application en utilisant nos données comme fond de carte, mais je ne peux alors utiliser aucun des fonds de carte d’Esri. Lorsque je le fais, mes données sont reprojetées en Web Mercator.

Anonymous User · Answer

I agree with Peter - Web Mercator (WKID 3857) is not recommended for making measurements on a printed copy using the graphical scalebar because of its distortions, especially closer to the poles. Measuring distances and areas when your map uses the Mercator projection   However, you can request the Esri basemaps in a different projection, if you are working on creating a viewer. You just request them as a dynamic map service (now called a map image layer) and add them as a layer to the map object.  They will render slower and you will notice the jpg compression. However, it is possible to add Esri basemaps in your viewer in State Plane in this way, and State Plane if you are in the US is one the better choices in general if you will be making measurements based on the scalebar. Otherwise, choose your projection based on which you need to be most accurate (distance, direction, shape, and/or area).  How to choose a projection

Also note, the Print widget in the WebApp Builder actually has an option to set the printout result to any projection.  Such as state plane.  However, I was unable to get it to work, it appears at the moment to have some sort of bug with reprojecting which I'm waiting to hear back on:   https://community.esri.com/ideas/10523#comment-76402

Anonymous User · Answer

Hi Kennie Harris‌,

My understanding is that it is not possible to reproject Esri Basemaps in ArcGIS Online. They will always be in Web Mercator. However, when using a Basemap in a State Plane projection, you can add an imagery layer made accessible in ArcGIS Online and the Web Map will remain in the State Plane projection. If you are able to find fine-scale imagery for your area in ArcGIS Online this may work.

Alternatively if you have ArcGIS Enterprise you can publish a cached Map Service or Image Service in your State Plane projection and use this as the Basemap.

Hope this helps,

Peter