Disclaimer, I'm a dev at Rackspace and helped run 2015's instance of the internal conference example linked in OP.
Speaking only from my own experience, this kind of internal dev conference can be especially useful for large companies (like Rackspace) that have teams of developers spread across the world, who may never otherwise work side-by-side. You mentioned management buy-in: a key selling point is that even outside of the talks+workshops, an internal con provides a discrete, intentional space for these spread-out teams to work together for a few days, outside of the pipeline of their "regular" work. Essentially you are bringing the benefit of hackathons & sprints to internal projects, using the structure of a conference for framing.
As far as "how to get devs to speak" -- lots of devs do like speaking (or teaching workshops), and maybe it's easier to do that for an audience of immediate peers and coworkers? But for many public speaking IS hard, and a way to mitigate that barrier is to consider the idea of an unconference [1]. When you move away from the standard tech talk format (stage, mic, podium, etc) and towards an "unconference session" (white board, circle of chairs, participant-set agenda), you can get a surprisingly high level of participation.
I'd be interested to hear of any experiences with this kind of thing at a smaller company, but essentially I think the core advantages (sprints, intentional technical discussion, knowledge exchange/training) are things that can be scaled up or down at will.
That doesn't really make any sense: "trap streets" make sense and are used in, say, the base map that you see when viewing a Google map (that is, in the raster data). But why would Google bother putting a trap street into their own (proprietary) street data used for routing? Unless you are saying that Google Maps "directed" you in the sense that you were looking at a printout of a map that included a trap street, not actually a turn-by-turn.
While notaddicted's reply can also be useful to you, I think the part of the puzzle that you are missing is "georeferencing". From your example, with a raster (bitmap, image) map of the US: the part where you start connecting that to lat/lon is georeferencing. Essentially, you want to tie a spatial reference to your image, so that the raster's state boundaries will correspond to state boundaries on a "real" map. You can think of it as pinning an image you know nothing about to a map you do know something about, and then copying the information from known to unknown.
There are plenty of ways to georeference an image. The easiest would be to use something like QGIS or GRASS (both opensource GIS software). You will need existing spatial data to base your (as of now, non-spatial) map on: a shapefile of the state boundaries would work great.
Once you've wrapped your head around georeferencing and the idea of spatial vs nonspatial data, you will probably get more out of the mapsfromscratch tutorial.
Speaking only from my own experience, this kind of internal dev conference can be especially useful for large companies (like Rackspace) that have teams of developers spread across the world, who may never otherwise work side-by-side. You mentioned management buy-in: a key selling point is that even outside of the talks+workshops, an internal con provides a discrete, intentional space for these spread-out teams to work together for a few days, outside of the pipeline of their "regular" work. Essentially you are bringing the benefit of hackathons & sprints to internal projects, using the structure of a conference for framing.
As far as "how to get devs to speak" -- lots of devs do like speaking (or teaching workshops), and maybe it's easier to do that for an audience of immediate peers and coworkers? But for many public speaking IS hard, and a way to mitigate that barrier is to consider the idea of an unconference [1]. When you move away from the standard tech talk format (stage, mic, podium, etc) and towards an "unconference session" (white board, circle of chairs, participant-set agenda), you can get a surprisingly high level of participation.
I'd be interested to hear of any experiences with this kind of thing at a smaller company, but essentially I think the core advantages (sprints, intentional technical discussion, knowledge exchange/training) are things that can be scaled up or down at will.
1) e.g., http://transparencycamp.org/about/tips/