Map question

[Muhammad2923]

Hi guys have a question how do satellite image like on Maxar and Google differ from maps , or is the satellite image a form of a map?
Also how do basemaps differ from maps? https://www.maxar.com/products/imagery-basemaps

[Redrobes]

Well an image can be a map. But usually the main difference is that a map is a representation of space that has been curated or drawn to show specific information. So where a satellite image will show a place it also shows everything visual in that space. With a map its as much about what you dont show as what you do. All of the extranous useless and distracting information has been removed leaving the aspect of the map that you want to present.

So for the most basic example, you might label towns and cities on a satellite image. Now the map shows where places are but it would be up to you to infer from the image where you might be able to travel to get from one place to another. The map might then put in country and regional boundaries and road systems. Now you can use the map to figure out your most efficient way to get from one place to the next using the roads listed.

The satellite image is really useful because most people can use it to interpret it themselves to provide the information that they need. A map is where the cartographer has done that for you and presented it in a way that makes the information readily available. Exactly what information you want to convery in a map depends on the purpose of the map.

Another thing a map generally provides over a satellite photo is a scale. Now you can measure distances on the photo and work out various things like how long it would take you to travel across it. For aerial photos more than satellite, the photo has to be ortho-rectified. That is to say it has to be projected onto the page in such a way that all of the scale at every part of the photo is the same and possibly aligned with north or some grid projection. I would bet that the Maxar images have already been processed in this way but if you had aerial photos from a plane at a lower altitude than satellites provide, then edges of a photo are of compressed scale compared to the centre.

Its a certainty that Google satellite imagery definitely has been processed. If you get a GPS out and compare the image to the ground readings then they are usually correct except when you go on top of a bridge, tall building or similar where you will find that, due to the vertical offset of the bridge, its now a few metres out from what your GPS tells you. This is because in most cases the higher res photos were taken from a plane at some angle so that the top of a building moves laterally in the photo compared to the bottom of it.

But obviously satellite imagery, being roughly ortho-rectified from such altitude, and showing the reality of whats in a location, makes a really useful starting point for making a map.

[Muhammad2923]

So all the orthorectified maps on google are satellite images turning into maps?
Still have a question on the basemaps vs maps. Are basemaps a different type of map than a map?
https://www.maxar.com/products/imagery-basemaps
https://www.arcgis.com/home/group.ht...s=maps#content