Grid is not showing exact Lat-Lon of the map image in QGIS Printcomposer?

Question

I am trying to print a map using QGIS 3.6.

My study area is situated within 23.55’42”N 89.27’43”E to 23.55’47”N 89.95’01”E. I am using a Landsat image as map image, The map projection is EPSG 32645 (UTM).

When I am trying to add a grid to the map, the Lat and Lon point starts from 0.00 N and 0.00 E instead of my image's Lat-Lon value.

The second problem is, when I'm trying to input the interval units in map units, I am having black spots instead of values.

Here I have attached the screenshots:

Answer 1

If you have a projected map, e.g. a UTM-Projected polygon, but you want to draw a grid showing latitude and longitude you need to change your grid's CRS to EPSG:4326.

1. UTM Grid

If you set up an UTM grid, your map units will be meters. An interval of x50000 and y50000 shows a grid every 50km. To use this, you must set your grid's CRS to UTM, e.g. EPSG:32645

2. Lat Lng Grid

If you set up a LatLon grid, your map units will be degree. An interval of x1 and y1 shows a grid every 1°. Distance in meters depends on your location. To use this, you must set your grid's CRS to EPSG:4326.

3. Both

Of course you can also use several grids at the same time:

If you are using centimeters as unit, then you will have a local "CRS" starting with 0 at your lower left corner, drawing a grid every few centimeter, depending on your interval. Same goes for millimeters as unit.