There are a few free Surveying programs available for the  HP-33s and HP-35s calculators. Their only drawback is that you have to key in the programs yourself since neither calculator has an alternate input option.  

HP-33s
   
  https://melbard.com   These are a collection of programs written by Al Melbard, a former Surveying Instructor at Milwaukee Area Technical College. They're a bit older, but still useful if you have a HP-33s.
HP-33s & HP-35s
   
  MN DOT   The Minnesota Dept of Transportation has developed a number of software tools including packages for the HP-33s and the HP-35s. Both packages are pretty extensive. 
 

Wollindina Media
   33s   35s

 

I've not tried Wollindina's programs but have heard they are petty good.
They have a broad survey software collection.

 

A few years ago, I downloaded an HP-35s emulator for Windows and manually keyed in the MN DOT HP-35s surveying package for it. That allows me to run a fully functional HP-35s on my computer and use it as a calculator or run the MN DOT software.

 If you would like to run an HP-35s emulation on your Windows computer with the MN DOT software follow these instructions

1. Download the emulator at  https://www.educalc.net/page/2336231/

Unzip the installation file and run it. 

2. You can key in the MN DOT software manually or save yourself the hassle by downloading my program file: MNDOT.ep

You must load the MNDOT.ep file the first time you run the emulator; it should load automatically on subsequent runs.

Calculator | Load

Navigate to and select the MNDOT.ep file

3. Go to MN DOT, open the menu for the HP35s software, and download either the HP35s Guide or the HP35s Programs pdf file. The first shows instructions for running the programs, the second also includes program listings.

4. The emulator comes with a few skins to change its size and appearance. 

Tool | Select Skin      (I like Medium 35s.)

MN DOT doesn't provide program support nor assume liability for their use, so you're on your own. The programs are relatively simple to run as long as you pay attention to their instructions. 

Jerry Mahun, 24 Feb 2024