Garmin Basecamp vs Garmin Explore vs CalTopo

At least some of what you want can be achieved in Garmin Basecamp, the Garmin maps you have on your 66i can be loaded onto your computer so that they can be used without having your 66i connected to the computer, there are several ways to do this

1. When downloading maps using Garmin Express (free updated or purchased maps), there is an option to download to the computer see below: -
   
   
   
   Any map that is downloaded to the computer will be available in Basecamp without the 66i being connected
   
   
2. Any Flash drive connected to your computer will act like your 66i, so if you create a folder on the Flash drive called Garmin and copy the *img file from your 66i to this flash drive, Basecamp will 'see' the maps on the Flash drive, e.g copy files [66i] /Garmin/My-Map1.img or [66i MicroSD] /Garmin/My Map2.img or [GPS/Satnav] /Map/My-Map3.img to [Flash Drive] /Garmin My-Map1.img + /Garmin My-Map2.img + /Garmin My-Map3.img
   
   
3. You can create a Virtual Flash drive on your computer hard disk that emulates a Flash drive and then use this drive as you would in 2) above
   
   
4. You can copy *.img files to a folder on your computer and then 'register' them in the computer's registry so that Garmin Bascamp will 'see' them, this is what Garmin Express does when downloading to a computer drive, the registration process is usually carried out by a batch file, here is an example batch file, please note this file would need to be tailored for each map installation

Code:

echo off
echo -
echo -
echo -  This batch will install map for Mapsource
echo -
echo -  Map:  "TT STD British Isles+Contours"
echo -  FID:  1232
echo -  PID:  1232
echo -
echo -  Press Enter to continue or Ctrl-C to abort.
echo -
pause

if exist "%~dp0mapset.img" goto :INSTREG
echo File missing: mapset.img, aborting install.
pause
exit 1

:INSTREG
echo Adding registry keys.

set KEY=HKLM\SOFTWARE\Wow6432Node\Garmin\MapSource
if %PROCESSOR_ARCHITECTURE% == AMD64 goto key_ok
set KEY=HKLM\SOFTWARE\Garmin\MapSource
:key_ok

reg ADD %KEY%\Families\FAMILY_1232 /v ID /t REG_BINARY /d D004 /f
if exist "%~dp0mapset_mdr.img" (
   reg ADD %KEY%\Families\FAMILY_1232 /v IDX /t REG_SZ /d "%~dp0mapset.mdx" /f
   reg ADD %KEY%\Families\FAMILY_1232 /v MDR /t REG_SZ /d "%~dp0mapset_mdr.img" /f
)
if exist "%~dp0mapset.typ" reg ADD %KEY%\Families\FAMILY_1232 /v TYP /t REG_SZ /d "%~dp0mapset.typ" /f
reg ADD %KEY%\Families\FAMILY_1232\1232 /v Loc /t REG_SZ /d "%~dp0\" /f
reg ADD %KEY%\Families\FAMILY_1232\1232 /v Bmap /t REG_SZ /d "%~dp0mapset.img" /f
reg ADD %KEY%\Families\FAMILY_1232\1232 /v Tdb /t REG_SZ /d "%~dp0mapset.tdb" /f
pause
exit 0