# working with worldpop

population dynamics

Question 1:

copy the code below into the earth engine code editor and hit run

```// import worldpop data
var wp = ee.Image("WorldPop/GP/100m/pop/KHM_2020");

```

Try to answer the following questions

1. What is the date of the image?
2. what is the spatial resolution?
3. What is the unit of the data?

Question 2:

copy the code below into the earth engine code editor and hit run

```// import worldpop data
var wp2000 = ee.Image("WorldPop/GP/100m/pop/KHM_2000");

// import worldpop data
var wp2020 = ee.Image("WorldPop/GP/100m/pop/KHM_2020");
```

Try to answer the following questions

1. where do we see the main differences in the imagery?
2. do you see any image artifacts?

Question 3:

Draw an area around Phnom Penh

copy the code below into the previous code and hit run

```print(wp2000.reduceRegion({reducer:ee.Reducer.sum(),geometry:aoi,scale:100}));
print(wp2020.reduceRegion({reducer:ee.Reducer.sum(),geometry:aoi,scale:100}));
```

Try to answer the following questions

1. why do we use the sum in this example?
2. what is the estimated population in Siem Reap?

Question 4

Use the code below to calculate the population for each province

```// define the countries of interest

// import worldpop data
var wp = ee.ImageCollection("WorldPop/GP/100m/pop").filterBounds(cambodia);

// set the start and end dates
var start = ee.Date.fromYMD(2020,1,1);
var end = ee.Date.fromYMD(2020,12,31);

// filter for the period of interest
var wp2020 = ee.Image(wp.filterDate(start,end).mean());

// clip for the area of interest
wp2020 = wp2020.clip(cambodia);

var totalPopulation = wp2020.reduceRegion({reducer:ee.Reducer.sum(),scale:100,geometry:cambodia,maxPixels:1e13})
print("Total Population:",totalPopulation)

var chart =
ui.Chart.image.byRegion
({
image:wp2020,
regions: cambodia,
reducer: ee.Reducer.sum(),
scale: 100,
xProperty: 'NAME_1'
})
.setSeriesNames(['population'])
.setChartType('ColumnChart')
.setOptions({
title: 'population per provinces',
hAxis: {title: 'Date', titleTextStyle: {italic: false, bold: true}},
vAxis: {
title: 'total population',
titleTextStyle: {italic: false, bold: true}
},
lineWidth: 5,
colors: ['e37d05'],
curveType: 'function'
});

print(chart);
```