All language subtitles for 03_scale-annotation-and-visibility.en

I'm sure you've probably noticed when you're using a web map that as you zoom in,

the amount of information that's included on the map changes.

I find this kind of a fascinating thing is that the people that

designed these web maps had to make those decisions about,

well, at this zoom level,

what do we include?

What's important to people? And what do we leave out?

Then sometimes, it's useful to compare

different web mapping services like say Google Maps,

versus Esri's maps, just to see what kind of differences they made.

Some decisions will be made by one company that are different from another,

and I'm just curious in terms of map design.

What the thought process was that they went through,

what's the resulting map looks like.

So, let's just have a quick look at this.

So, in terms of scale and annotation,

here we're looking at a map at Level 7,

and so you can see things like they've got states labeled,

some towns or cities I should say Pittsburgh,

major bodies of water and so on.

If we go in, this is actually a screenshot so this is Zoom Level 11.

We're now seeing smaller towns,

sort of more roads,

more detail being added,

and if we zoom in again,

this is Level 17 we can see a lot more detail.

So, we're actually getting things like paths through Central Park,

individually street labels, you see

there as well as building footprints, all kinds of things.

So, different levels of detail at different scales.

If we zoom in even more,

you'll see here that we have more building footprints.

These are probably bits of vegetation.

It's been a long time since I've been to Central Park,

I don't remember, contour lines,

and so it's just useful to kind of have a look at this, look at the annotation,

what design decisions were made,

how this relates to scale and web mapping in particular.

When looking at web maps,

it's interesting to look at

the different design decisions that were made for different base maps.

So, for example here, this is Esri's default base map

which is known as the topographic one that's what they call it,

and so you can see the style, the design,

the type of content that's their versus a different base map from Esri.

This one is called Streets.

So, it has a very different look to it,

I think I'm assuming that the emphasis here was on navigation.

So, the streets were more prominent.

There's less detail in some ways,

although we do have things like outlines of trees and there are building footprints,

but they're a little more subtle than the other one perhaps.

This is a different base map.

This is called The Open Street Map version which is different again.

It has very different style choices as well as the type of content that's included.

We can have a satellite image as our base map with no annotation whatsoever.

Then there's another version of the base map with

some annotation but I'm assuming the reason that there's not

much is that they don't want it to get in the way of you

being able to visually interpret the image itself.

So, that's just a quick way of looking at,

I think I've probably done this a lot through these different segments,

but I'm always trying to encourage you to think about,

well, what does somebody else do?

Why they do it that way?

Do I like it? Is this something that would change?

Just be more critical in

a good way about what it is that you're looking at in terms of different maps.

When you're creating your own maps,

whether they're through ArcGIS online, or through ArcMap.

You can set the scale at which different features become visible or invisible,

pretty much in the same way that you would with

a web map that you've seen the choices that someone else has made.

So, for example here in ArcGIS online,

or AGOL for short,

you can set the scale visibility ranges they would call it.

So, if you click on the little three circles here,

you'll see that you can say

Set Visibility Range and then there's a slider here for this particular.

So, this is for the volcanoes feature class,

and you can say that it's only visible when you zoom

in to a certain scale or it becomes invisible,

and you zoom out to a certain scale,

and so that's very useful in terms of

controlling the amount of information that somebody sees at a particular map scale.

You can do this in ArcMap as well.

You can set the scale range if you go under layer properties here,

and you'll see "Don't show layer when zoomed out beyond," in this case 1-1,000,000.

You could set it to be beyond 1-10 million,

so these can be whatever you want.

I'm just using these as examples and the idea

is that you're again you're trying to control

the amount of information that somebody sees.

So you don't overwhelm them with

too much information at a particular map scale that's really not that appropriate for it.

So for example, if you're asking why set visibility range?

Well, I like this example,

I made this one, is that as I said, okay,

I'm going to make it so that you can see

every river and creek that's in this data set for the entire United States,

and say, okay, here's a map of all the water routes in the United States,

and of course it's completely useless.

It's just this big blue blob at this map scale.

So, what we should be doing is setting

the visibility range or the zoom layering is another term that's used for this,

so that at this map scale,

you would not be able to see all of these features,

because it's really not useful.

It's not helping anybody to see them at this map scale.

But if we set it so that they do become visible when we zoom in,

then of course this would be completely appropriate as you can see

the individual features at a scale where it's appropriate,

where it's like, okay,

yeah, it makes sense to me.

It's not one big blue blob. That's all it really is.

It is useful, it's a design question or decision that you have to make

when you're making digital maps or ones

that are going to be seen by people at different scales.

There's an interesting relationship between symbology and map scale.

Something that comes up when we're talking

about this is that when you draw a line on a map,

it's probably going to be wider or thicker than it really represents on the ground.

A rule of thumb,

this goes for printed maps more than ones on screen,

but I imagine it's pretty much the same.

So, when you're printing a map,

anything thinner than 0.5 millimeters,

half a millimeter is not going to print very well.

So, that's why I think this rule of thumb has come up the way it has,

is that if you have a line that's that thin,

so half a millimeter wide,

which is suppose things you're going to get.

Let's just put it that way. Then at a scale of 1-50,000,

that represents 25,000 millimeters on the ground which is actually 25 meters.

If that's a road or a sidewalk or something like that, you think, okay,

well, actually, if it's a road,

it's not too bad, 25 meters.

If it's a sidewalk, there are very few sidewalks that are 25 meters wide.

But if you take that same thickness of line,

0.5 millimeters, and put it on a map at 1-250,000,

that same thickness of line now represents 125 meters across,

and at 1-10 million,

it's 5,000 meters across.

Now, this may seem like I'm kind of being a bit ridiculous,

but just think about it for a second.

Let's say if you have that thin,

thin line that you're using to represent say a road on a map of,

this would be at that scale sort of maybe half of the United States or something,

is that you're saying that that road is five kilometers wide.

Not long, wide.

Which of course is ridiculous.

But I'm just trying to point out that there is

this kind of design decision that's made is that there's

an exaggeration of features that has to be made in order to

symbolize them correctly when you're simplifying and

generalizing the real-world to put it on a map,

compromises are going to have to be made.

So, this is just a way of kind of pointing that out that there's

a relationship between the size of the symbol and the map scale.

Scale also affects how things are represented.

So, here we have a map of I would call this a regional scale,

where we can see Philadelphia,

New York, and so on.

At this map scale,

these are being shown as white circles with a black ring around it.

Now, if I zoomed in and still showed

that same symbol for those things at a larger map scale,

now would be kind of ridiculous, wouldn't it?

That makes no sense. So, the way that

a real world object is symbolized will be related to scale.

So, here you'll see that this is Washington,

this makes a little more sense,

is that we're now basically showing Washington as an area as opposed to a point.

So, if we're zoomed out,

an entire city might be shown as

just one point symbol with a little circle, when we zoom in,

we may decide to change that to an area

and of course here it's actually shown as a very large area,

and we might perhaps have a polygon,

say for the city limits or something like that,

shade that in order to be able to show where that actual city's located.

Okay. So, that's just a way of relating scale to symbology

which can change especially when you're using

digital maps and web maps or interactive dynamic kind of maps.