Making a GeoTIFF using Google Earth Data
There are a number of ways you can add your raster to GeoServer, all of these require you to know what the projection of your data is (probably EPSG:4326 or WGS84 lat/lon).
Possibly the simplest, just tell GeoServer what the projection is after adding the data to the store. When you publish the layer simply fill in the declared SRS as EPSG:4326 and select
force declaredunderneath. GeoServer will ignore it's "native" SRS guess and use your information.
You can convert your tiff + world file into a GeoTiff using GDAL's gdal_translate again you need to tell GDAL what projection you are using.
gdal_translate -a_srs original.tif newgeotif.tif
You can provide a
.prjfile which contains the WKT representation of the projection you need - you can download these from http://epgs.io so yours would this. Like the
.wldfile this side car file can be read by other programs to tell them what the projection is.